diff --git a/php/federator/api/fedusers/inbox.php b/php/federator/api/fedusers/inbox.php
index 9cb03e1..9ca8ca4 100644
--- a/php/federator/api/fedusers/inbox.php
+++ b/php/federator/api/fedusers/inbox.php
@@ -43,7 +43,7 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
     /**
      * handle post call
      *
-     * @param string|null $_user user to add data to inbox @unused-param
+     * @param string|null $_user user to add data to inbox
      * @return string|false response
      */
     public function post($_user)
@@ -107,6 +107,10 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
                 && (filter_var($receiver, FILTER_VALIDATE_URL) !== false);
         });
 
+        if (isset($_user)) {
+            $receivers[] = $dbh->real_escape_string($_user); // Add the target user to the receivers list
+        }
+
         // Special handling for Follow and Undo follow activities
         if (strtolower($inboxActivity->getType()) === 'follow') {
             // For Follow, the object should hold the target
@@ -126,6 +130,7 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
                 }
             }
         }
+        $ourDomain = $config['generic']['externaldomain'];
 
         foreach ($receivers as $receiver) {
             if ($receiver === '' || !is_string($receiver)) {
@@ -157,18 +162,19 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
                     $users = array_merge($users, array_column($followers, 'id'));
                 }
             } else {
-                $ourDomain = $config['generic']['externaldomain'];
                 // check if receiver is an actor url from our domain
-                if (!str_contains($receiver, $ourDomain)) {
+                if (!str_contains($receiver, $ourDomain) && $receiver !== $_user) {
                     continue;
                 }
-                $receiverName = basename((string) (parse_url($receiver, PHP_URL_PATH) ?? ''));
-                $ourDomain = parse_url($receiver, PHP_URL_HOST);
-                if ($receiverName === null || $ourDomain === null) {
-                    error_log("Inbox::post no receiverName or domain found for receiver: " . $receiver);
-                    continue;
+                if ($receiver !== $_user) {
+                    $receiverName = basename((string) (parse_url($receiver, PHP_URL_PATH) ?? ''));
+                    $ourDomain = parse_url($receiver, PHP_URL_HOST);
+                    if ($receiverName === null || $ourDomain === null) {
+                        error_log("Inbox::post no receiverName or domain found for receiver: " . $receiver);
+                        continue;
+                    }
+                    $receiver = $receiverName;
                 }
-                $receiver = $receiverName . '@' . $ourDomain;
                 try {
                     $localUser = \Federator\DIO\User::getUserByName(
                         $dbh,
@@ -209,6 +215,30 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
             ]);
             error_log("Inbox::post enqueued job for user: $user->id with token: $token");
         }
+        if (empty($users)) {
+            $type = strtolower($inboxActivity->getType());
+            if ($type === 'undo' || $type === 'delete') {
+                $token = \Resque::enqueue('inbox', 'Federator\\Jobs\\InboxJob', [
+                    'user' => $user->id,
+                    'recipientId' => "",
+                    'activity' => $inboxActivity->toObject(),
+                ]);
+                error_log("Inbox::post enqueued job for user: $user->id with token: $token");
+            } else {
+                error_log("Inbox::post no users found for activity, doing nothing: " . json_encode($inboxActivity, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT));
+            }
+        }
+
+        try {
+            $articleId = \Federator\DIO\Posts::getOriginalArticleId($dbh, $inboxActivity);
+            if ($articleId !== null) {
+                $connector->sendActivity($user, $inboxActivity);
+            }
+        } catch (\Throwable $e) {
+            error_log("Inbox::postForUser Error sending activity to connector. Exception: " . $e->getMessage());
+            return false;
+        }
+
         return "success";
     }
 
@@ -241,6 +271,56 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
             return false;
         }
 
+        $type = strtolower($inboxActivity->getType());
+
+        if ($_recipientId === '') {
+            if ($type === 'undo' || $type === 'delete') {
+                switch ($type) {
+                    case 'delete':
+                        // Delete Note/Post
+                        $object = $inboxActivity->getObject();
+                        if (is_string($object)) {
+                            \Federator\DIO\Posts::deletePost($dbh, $object);
+                        } elseif (is_object($object)) {
+                            $objectId = $object->getID();
+                            \Federator\DIO\Posts::deletePost($dbh, $objectId);
+                        } else {
+                            error_log("Inbox::postForUser Error in Delete Post for user $user->id, object is not a string or object");
+                            error_log(" object of type " . gettype($object));
+                            return false;
+                        }
+                        break;
+
+                    case 'undo':
+                        $object = $inboxActivity->getObject();
+                        if (is_object($object)) {
+                            switch (strtolower($object->getType())) {
+                                case 'like':
+                                case 'dislike':
+                                    // Undo Like/Dislike (remove like/dislike)
+                                    $targetId = $object->getID();
+                                    // \Federator\DIO\Votes::removeVote($dbh, $user->id, $targetId, 'dislike');
+                                    \Federator\DIO\Posts::deletePost($dbh, $targetId);
+                                    break;
+                                case 'note':
+                                case 'article':
+                                    // Undo Note (remove note)
+                                    $noteId = $object->getID();
+                                    \Federator\DIO\Posts::deletePost($dbh, $noteId);
+                                    break;
+                            }
+                        }
+                        break;
+
+                    default:
+                        error_log("Inbox::postForUser Unhandled activity type $type for user $user->id");
+                        break;
+                }
+
+                return true;
+            }
+        }
+
         $atPos = strpos($_recipientId, '@');
         if ($atPos !== false) {
             $_recipientId = substr($_recipientId, 0, $atPos);
@@ -266,18 +346,16 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
             FILE_APPEND
         );
 
-        $type = $inboxActivity->getType();
-
         switch ($type) {
-            case 'Follow':
+            case 'follow':
                 $success = \Federator\DIO\Followers::addExternalFollow($dbh, $inboxActivity->getID(), $user->id, $recipient->id);
 
                 if ($success === false) {
-                    error_log("Inbox::postForUser: Failed to add follower for user $user->id");
+                    error_log("Inbox::postForUser Failed to add follower for user $user->id");
                 }
                 break;
 
-            case 'Delete':
+            case 'delete':
                 // Delete Note/Post
                 $object = $inboxActivity->getObject();
                 if (is_string($object)) {
@@ -288,11 +366,11 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
                 }
                 break;
 
-            case 'Undo':
+            case 'undo':
                 $object = $inboxActivity->getObject();
                 if (is_object($object)) {
-                    switch ($object->getType()) {
-                        case 'Follow':
+                    switch (strtolower($object->getType())) {
+                        case 'follow':
                             $success = false;
                             if ($object instanceof \Federator\Data\ActivityPub\Common\Activity) {
                                 $actor = $object->getAActor();
@@ -301,75 +379,60 @@ class Inbox implements \Federator\Api\FedUsers\FedUsersInterface
                                 }
                             }
                             if ($success === false) {
-                                error_log("Inbox::postForUser: Failed to remove follower for user $user->id");
+                                error_log("Inbox::postForUser Failed to remove follower for user $user->id");
                             }
                             break;
-                        case 'Like':
-                            // Undo Like (remove like)
-                            if (method_exists($object, 'getObject')) {
-                                $targetId = $object->getObject();
-                                if (is_string($targetId)) {
-                                    // \Federator\DIO\Votes::removeVote($dbh, $user->id, $targetId, 'like');
-                                    \Federator\DIO\Posts::deletePost($dbh, $targetId);
-                                } else {
-                                    error_log("Inbox::postForUser: Error in Undo Like for user $user->id, targetId is not a string");
-                                }
-                            }
+                        case 'like':
+                        case 'dislike':
+                            // Undo Like/Dislike (remove like/dislike)
+                            $targetId = $object->getID();
+                            // \Federator\DIO\Votes::removeVote($dbh, $user->id, $targetId, 'dislike');
+                            \Federator\DIO\Posts::deletePost($dbh, $targetId);
                             break;
-                        case 'Dislike':
-                            // Undo Dislike (remove dislike)
-                            if (method_exists($object, 'getObject')) {
-                                $targetId = $object->getObject();
-                                if (is_string($targetId)) {
-                                    // \Federator\DIO\Votes::removeVote($dbh, $user->id, $targetId, 'dislike');
-                                    \Federator\DIO\Posts::deletePost($dbh, $targetId);
-                                } else {
-                                    error_log("Inbox::postForUser: Error in Undo Dislike for user $user->id, targetId is not a string");
-                                }
-                            }
-                            break;
-                        case 'Note':
+                        case 'note':
                             // Undo Note (remove note)
-                            if (method_exists($object, 'getID')) {
-                                $noteId = $object->getID();
-                                \Federator\DIO\Posts::deletePost($dbh, $noteId);
-                            }
+                            $noteId = $object->getID();
+                            \Federator\DIO\Posts::deletePost($dbh, $noteId);
                             break;
                     }
                 }
                 break;
 
-            case 'Like':
-                // Add Like
-                $targetId = $inboxActivity->getObject();
-                if (is_string($targetId)) {
-                    // \Federator\DIO\Votes::addVote($dbh, $user->id, $targetId, 'like');
-                    \Federator\DIO\Posts::savePost($dbh, $user->id, $inboxActivity);
-                } else {
-                    error_log("Inbox::postForUser: Error in Add Like for user $user->id, targetId is not a string");
-                    return false;
-                }
-                break;
-
-            case 'Dislike':
-                // Add Dislike
+            case 'like':
+            case 'dislike':
+                // Add Like/Dislike
                 $targetId = $inboxActivity->getObject();
                 if (is_string($targetId)) {
                     // \Federator\DIO\Votes::addVote($dbh, $user->id, $targetId, 'dislike');
                     \Federator\DIO\Posts::savePost($dbh, $user->id, $inboxActivity);
                 } else {
-                    error_log("Inbox::postForUser: Error in Add Dislike for user $user->id, targetId is not a string");
+                    error_log("Inbox::postForUser Error in Add Like/Dislike for user $user->id, targetId is not a string");
                     return false;
                 }
                 break;
 
-            case 'Note':
-                // Post Note
-                \Federator\DIO\Posts::savePost($dbh, $user->id, $inboxActivity);
+            case 'create':
+            case 'update':
+                $object = $inboxActivity->getObject();
+                if (is_object($object)) {
+                    switch (strtolower($object->getType())) {
+                        case 'note':
+                            \Federator\DIO\Posts::savePost($dbh, $user->id, $inboxActivity);
+
+                            break;
+                        case 'article':
+                            \Federator\DIO\Posts::savePost($dbh, $user->id, $inboxActivity);
+
+                            break;
+                        default:
+                            \Federator\DIO\Posts::savePost($dbh, $user->id, $inboxActivity);
+                            break;
+                    }
+                }
                 break;
 
             default:
-                error_log("Inbox::postForUser: Unhandled activity type $type for user $user->id");
+                error_log("Inbox::postForUser Unhandled activity type $type for user $user->id");
                 break;
         }
 
diff --git a/php/federator/api/v1/newcontent.php b/php/federator/api/v1/newcontent.php
index 57a2c14..816afe0 100644
--- a/php/federator/api/v1/newcontent.php
+++ b/php/federator/api/v1/newcontent.php
@@ -100,8 +100,9 @@ class NewContent implements \Federator\Api\APIInterface
             return false;
         }
 
+        $articleId = "";
         if (isset($allHeaders['X-Sender'])) {
-            $newActivity = $connector->jsonToActivity($input);
+            $newActivity = $connector->jsonToActivity($input, $articleId);
         } else {
             error_log("NewContent::post No X-Sender header found");
             return false;
@@ -212,6 +213,7 @@ class NewContent implements \Federator\Api\APIInterface
                 'user' => $posterName,
                 'recipientId' => $receiver,
                 'activity' => $newActivity->toObject(),
+                'articleId' => $articleId,
             ]);
             error_log("Inbox::post enqueued job for receiver: $receiver with token: $token");
         }
@@ -232,9 +234,11 @@ class NewContent implements \Federator\Api\APIInterface
      * @param string $_user user that triggered the post
      * @param string $_recipientId recipient of the post
      * @param \Federator\Data\ActivityPub\Common\Activity $newActivity the activity that we received
+     * @param string $articleId the original id of the article (if applicable)
+     *                           (used to identify the article in the remote system)
      * @return boolean response
      */
-    public static function postForUser($dbh, $connector, $cache, $host, $_user, $_recipientId, $newActivity)
+    public static function postForUser($dbh, $connector, $cache, $host, $_user, $_recipientId, $newActivity, $articleId)
     {
         if (!isset($_user)) {
             error_log("NewContent::postForUser no user given");
@@ -272,10 +276,10 @@ class NewContent implements \Federator\Api\APIInterface
             FILE_APPEND
         );
 
-        $type = $newActivity->getType();
+        $type = strtolower($newActivity->getType());
 
         switch ($type) {
-            case 'Follow':
+            case 'follow':
                 // $success = false;
                 $actor = $newActivity->getAActor();
                 if ($actor !== '') {
@@ -293,7 +297,7 @@ class NewContent implements \Federator\Api\APIInterface
                 } */
                 break;
 
-            case 'Delete':
+            case 'delete':
                 // Delete Note/Post
                 $object = $newActivity->getObject();
                 if (is_string($object)) {
@@ -304,11 +308,11 @@ class NewContent implements \Federator\Api\APIInterface
                 }
                 break;
 
-            case 'Undo':
+            case 'undo':
                 $object = $newActivity->getObject();
                 if (is_object($object)) {
-                    switch ($object->getType()) {
-                        case 'Follow':
+                    switch (strtolower($object->getType())) {
+                        case 'follow':
                             $success = false;
                             if ($object instanceof \Federator\Data\ActivityPub\Common\Activity) {
                                 $actor = $object->getAActor();
@@ -332,8 +336,8 @@ class NewContent implements \Federator\Api\APIInterface
                                 error_log("NewContent::postForUser Failed to remove follower for user $user->id");
                             }
                             break;
-                        case 'Like':
-                        case 'Dislike':
+                        case 'like':
+                        case 'dislike':
                             if (method_exists($object, 'getObject')) {
                                 $targetId = $object->getObject();
                                 if (is_string($targetId)) {
@@ -344,13 +348,13 @@ class NewContent implements \Federator\Api\APIInterface
                                 }
                             }
                             break;
-                        case 'Note':
+                        case 'note':
                             // Undo Note (remove note)
                             $noteId = $object->getID();
                             \Federator\DIO\Posts::deletePost($dbh, $noteId);
 
                             break;
-                        case 'Article':
+                        case 'article':
                             $articleId = $object->getID();
                             \Federator\DIO\Posts::deletePost($dbh, $articleId);
                             // also remove latest saved article-update
@@ -381,30 +385,30 @@ class NewContent implements \Federator\Api\APIInterface
                 }
                 break;
 
-            case 'Like':
-            case 'Dislike':
+            case 'like':
+            case 'dislike':
                 // Add Like/Dislike
                 $targetId = $newActivity->getObject();
                 if (is_string($targetId)) {
                     // \Federator\DIO\Votes::addVote($dbh, $user->id, $targetId, 'like');
-                    \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity);
+                    \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity, $articleId);
                 } else {
                     error_log("NewContent::postForUser Error in Add Like/Dislike for recipient $recipient->id, targetId is not a string");
                     return false;
                 }
                 break;
 
-            case 'Create':
-            case 'Update':
+            case 'create':
+            case 'update':
                 $object = $newActivity->getObject();
                 if (is_object($object)) {
-                    switch ($object->getType()) {
-                        case 'Note':
-                            \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity);
+                    switch (strtolower($object->getType())) {
+                        case 'note':
+                            \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity, $articleId);
 
                             break;
-                        case 'Article':
-                            \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity);
+                        case 'article':
+                            \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity, $articleId);
 
                             $idPart = strrchr($recipient->id, '@');
                             if ($idPart === false) {
@@ -423,7 +427,7 @@ class NewContent implements \Federator\Api\APIInterface
 
                             break;
                         default:
-                            \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity);
+                            \Federator\DIO\Posts::savePost($dbh, $user->id, $newActivity, $articleId);
                             break;
                     }
                 }
@@ -531,7 +535,6 @@ class NewContent implements \Federator\Api\APIInterface
         $response = curl_exec($ch);
         curl_close($ch);
 
-        // Log the response for debugging if needed
         if ($response === false) {
             throw new \Exception("Failed to send activity: " . curl_error($ch));
         } else {
diff --git a/php/federator/connector/connector.php b/php/federator/connector/connector.php
index f02c02e..c51e42a 100644
--- a/php/federator/connector/connector.php
+++ b/php/federator/connector/connector.php
@@ -70,9 +70,20 @@ interface Connector
      * Convert jsonData to Activity format
      *
      * @param array<string, mixed> $jsonData the json data from our platfrom
+     * @param string $articleId the original id of the article (if applicable)
+     *                           (used to identify the article in the remote system)
      * @return \Federator\Data\ActivityPub\Common\Activity|false
      */
-    public function jsonToActivity(array $jsonData);
+    public function jsonToActivity(array $jsonData, &$articleId);
+
+    /**
+     * send target-friendly json from ActivityPub activity
+     *
+     * @param \Federator\Data\FedUser $sender the user of the sender
+     * @param \Federator\Data\ActivityPub\Common\Activity $activity the activity
+     * @return boolean did we successfully send the activity?
+     */
+    public function sendActivity($sender, $activity);
 
     /**
      * check if the headers include a valid signature
diff --git a/php/federator/data/activitypub/common/delete.php b/php/federator/data/activitypub/common/delete.php
index bffb89f..aa23167 100644
--- a/php/federator/data/activitypub/common/delete.php
+++ b/php/federator/data/activitypub/common/delete.php
@@ -10,17 +10,6 @@ namespace Federator\Data\ActivityPub\Common;
 
 class Delete extends Activity
 {
-    /**
-     * object overwrite
-     * @var string
-     */
-    private $object = "";
-
-    public function setFObject(string $object): void
-    {
-        $this->object = $object;
-    }
-
     public function __construct()
     {
         parent::__construct('Delete');
@@ -33,10 +22,6 @@ class Delete extends Activity
      */
     public function fromJson($json): bool
     {
-        if (array_key_exists('object', $json)) {
-            $this->object = $json['object'];
-            unset($json['object']);
-        }
         return parent::fromJson($json);
     }
     /**
@@ -46,9 +31,6 @@ class Delete extends Activity
     public function toObject()
     {
         $return = parent::toObject();
-        if ($this->object !== "") {
-            $return['object'] = $this->object;
-        }
         return $return;
     }
 }
diff --git a/php/federator/data/activitypub/factory.php b/php/federator/data/activitypub/factory.php
index 1c92f1a..3fbf3c1 100644
--- a/php/federator/data/activitypub/factory.php
+++ b/php/federator/data/activitypub/factory.php
@@ -67,6 +67,9 @@ class Factory
             case 'Inbox':
                 $return = new Common\Inbox();
                 break;
+            case 'Tombstone':
+                $return = new Common\APObject("Tombstone");
+                break;
             /*case 'Question':
                 $return = new Common\Question();
                 break;
diff --git a/php/federator/dio/posts.php b/php/federator/dio/posts.php
index fbd33d7..5527482 100644
--- a/php/federator/dio/posts.php
+++ b/php/federator/dio/posts.php
@@ -216,13 +216,15 @@ class Posts
      * @param \mysqli $dbh
      * @param string $userId
      * @param \Federator\Data\ActivityPub\Common\Activity $post
+     * @param string|null $articleId the original id of the article
+     *                           (used to identify the source article in the remote system)
      * @return bool
      */
-    public static function savePost($dbh, $userId, $post)
+    public static function savePost($dbh, $userId, $post, $articleId = null)
     {
         $sql = 'INSERT INTO posts (
-                `id`, `url`, `user_id`, `actor`, `type`, `object`, `to`, `cc`, `published`
-            ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+                `id`, `url`, `user_id`, `actor`, `type`, `object`, `to`, `cc`, `published`, `article_id`
+            ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
             ON DUPLICATE KEY UPDATE
                 `url` = VALUES(`url`),
                 `user_id` = VALUES(`user_id`),
@@ -231,7 +233,8 @@ class Posts
                 `object` = VALUES(`object`),
                 `to` = VALUES(`to`),
                 `cc` = VALUES(`cc`),
-                `published` = VALUES(`published`)';
+                `published` = VALUES(`published`),
+                `article_id` = VALUES(`article_id`)';
         $stmt = $dbh->prepare($sql);
         if ($stmt === false) {
             throw new \Federator\Exceptions\ServerError();
@@ -248,6 +251,9 @@ class Posts
         if ($objectJson === false) {
             $objectJson = null;
         }
+        if (is_object($object)) {
+            $id = $object->getID();
+        }
         $to = $post->getTo();
         $cc = $post->getCC();
         $toJson = is_array($to) ? json_encode($to) : (is_string($to) ? json_encode([$to]) : null);
@@ -256,7 +262,7 @@ class Posts
         $publishedStr = $published ? gmdate('Y-m-d H:i:s', $published) : gmdate('Y-m-d H:i:s');
 
         $stmt->bind_param(
-            "sssssssss",
+            "ssssssssss",
             $id,
             $url,
             $userId,
@@ -265,7 +271,8 @@ class Posts
             $objectJson,
             $toJson,
             $ccJson,
-            $publishedStr
+            $publishedStr,
+            $articleId,
         );
         $result = $stmt->execute();
         $stmt->close();
@@ -292,4 +299,40 @@ class Posts
         $stmt->close();
         return $affectedRows > 0;
     }
+
+    /** retrieve original article id of post
+     *
+     * @param \mysqli $dbh
+     * @param \Federator\Data\ActivityPub\Common\Activity $post
+     * @return string|null
+     */
+    public static function getOriginalArticleId($dbh, $post)
+    {
+        $sql = 'SELECT `article_id` FROM posts WHERE id = ?';
+        $stmt = $dbh->prepare($sql);
+        if ($stmt === false) {
+            throw new \Federator\Exceptions\ServerError();
+        }
+        $id = $post->getID();
+        $object = $post->getObject();
+        if (is_object($object)) {
+            $inReplyTo = $object->getInReplyTo();
+            if ($inReplyTo !== "") {
+                $id = $inReplyTo; // Use inReplyTo as ID if it's a string
+            } else {
+                $id = $object->getObject();
+            }
+        } elseif (is_string($object)) {
+            $id = $object; // If object is a string, use it directly
+        }
+        $stmt->bind_param("s", $id);
+        $articleId = null;
+        $ret = $stmt->bind_result($articleId);
+        $stmt->execute();
+        if ($ret) {
+            $stmt->fetch();
+        }
+        $stmt->close();
+        return $articleId;
+    }
 }
diff --git a/php/federator/jobs/newContentJob.php b/php/federator/jobs/newContentJob.php
index 480fe32..2796e30 100644
--- a/php/federator/jobs/newContentJob.php
+++ b/php/federator/jobs/newContentJob.php
@@ -56,6 +56,7 @@ class NewContentJob extends \Federator\Api
         $user = $this->args['user'];
         $recipientId = $this->args['recipientId'];
         $activity = $this->args['activity'];
+        $articleId = $this->args['articleId'] ?? null;
 
         $activity = \Federator\Data\ActivityPub\Factory::newActivityFromJson($activity);
 
@@ -67,7 +68,7 @@ class NewContentJob extends \Federator\Api
 
         $ourUrl = 'https://' . $domain;
 
-        \Federator\Api\V1\NewContent::postForUser($this->dbh, $this->connector, $this->cache, $ourUrl, $user, $recipientId, $activity);
+        \Federator\Api\V1\NewContent::postForUser($this->dbh, $this->connector, $this->cache, $ourUrl, $user, $recipientId, $activity, $articleId);
         return true;
     }
 }
\ No newline at end of file
diff --git a/plugins/federator/contentnation.php b/plugins/federator/contentnation.php
index 1db8e6f..a77f846 100644
--- a/plugins/federator/contentnation.php
+++ b/plugins/federator/contentnation.php
@@ -368,9 +368,11 @@ class ContentNation implements Connector
      * Convert jsonData to Activity format
      *
      * @param array<string, mixed> $jsonData the json data from our platfrom
+     * @param string $articleId the original id of the article (if applicable)
+     *                           (used to identify the article in the remote system)
      * @return \Federator\Data\ActivityPub\Common\Activity|false
      */
-    public function jsonToActivity($jsonData)
+    public function jsonToActivity($jsonData, &$articleId)
     {
         $returnActivity = false;
         // Common fields for all activity types
@@ -482,6 +484,7 @@ class ContentNation implements Connector
                         $returnActivity->setID($ap['id']);
                         $returnActivity->setURL($ap['url']);
                     }
+                    $articleId = $jsonData['object']['id']; // Set the article ID for the activity
                     break;
 
                 case 'comment':
@@ -514,6 +517,7 @@ class ContentNation implements Connector
                         $returnActivity->setID($ap['id']);
                         $returnActivity->setURL($ap['url']);
                     }
+                    $articleId = $jsonData['object']['articleId']; // Set the article ID for the activity
                     break;
 
                 case 'vote':
@@ -548,6 +552,7 @@ class ContentNation implements Connector
                         $returnActivity->setID($ap['id']);
                         $returnActivity->setURL($ap['url']);
                     }
+                    $articleId = $jsonData['object']['articleId']; // Set the article ID for the activity
                     break;
 
                 default:
@@ -659,6 +664,250 @@ class ContentNation implements Connector
         return $returnJson;
     }
 
+    /**
+     * send CN-friendly json from ActivityPub activity
+     *
+     * @param \Federator\Data\FedUser $sender the user of the sender
+     * @param \Federator\Data\ActivityPub\Common\Activity $activity the activity
+     * @return boolean did we successfully send the activity?
+     */
+    public function sendActivity($sender, $activity)
+    {
+        $targetUrl = $this->service;
+        // Convert ActivityPub activity to ContentNation JSON format and retrieve target url
+        $jsonData = self::activityToJson($this->main->getDatabase(), $this->service, $activity, $targetUrl);
+
+        if ($jsonData === false) {
+            error_log("ContentNation::sendActivity failed to convert activity to JSON");
+            return false;
+        }
+
+        $json = json_encode($jsonData, JSON_UNESCAPED_SLASHES);
+
+        if ($json === false) {
+            throw new \Exception('Failed to encode JSON: ' . json_last_error_msg());
+        }
+        $digest = 'SHA-256=' . base64_encode(hash('sha256', $json, true));
+        $date = gmdate('D, d M Y H:i:s') . ' GMT';
+        $parsed = parse_url($targetUrl);
+        if ($parsed === false) {
+            throw new \Exception('Failed to parse URL: ' . $targetUrl);
+        }
+
+        if (!isset($parsed['host']) || !isset($parsed['path'])) {
+            throw new \Exception('Invalid target URL: missing host or path');
+        }
+        $extHost = $parsed['host'];
+        $path = $parsed['path'];
+
+        // Build the signature string
+        $signatureString = "(request-target): post {$path}\n" .
+            "host: {$extHost}\n" .
+            "date: {$date}\n" .
+            "digest: {$digest}";
+
+        $pKeyPath = PROJECT_ROOT . '/' . $this->main->getConfig()['keys']['federatorPrivateKeyPath'];
+        $privateKeyPem = file_get_contents($pKeyPath);
+        if ($privateKeyPem === false) {
+            http_response_code(500);
+            throw new \Federator\Exceptions\PermissionDenied("Private key couldn't be determined");
+        }
+
+        $pkeyId = openssl_pkey_get_private($privateKeyPem);
+
+        if ($pkeyId === false) {
+            throw new \Exception('Invalid private key');
+        }
+
+        openssl_sign($signatureString, $signature, $pkeyId, OPENSSL_ALGO_SHA256);
+        $signature_b64 = base64_encode($signature);
+
+        $signatureHeader = 'algorithm="rsa-sha256",headers="(request-target) host date digest",signature="' . $signature_b64 . '"';
+
+        $ch = curl_init($targetUrl);
+        if ($ch === false) {
+            throw new \Exception('Failed to initialize cURL');
+        }
+        $headers = [
+            'Host: ' . $extHost,
+            'Date: ' . $date,
+            'Digest: ' . $digest,
+            'Content-Type: application/json',
+            'Signature: ' . $signatureHeader,
+            'Accept: application/json',
+            'Username: ' . $sender->id,
+        ];
+
+        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+        curl_setopt($ch, CURLOPT_POST, true);
+        curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
+        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
+        $response = curl_exec($ch);
+        curl_close($ch);
+
+        if ($response === false) {
+            throw new \Exception("Failed to send activity: " . curl_error($ch));
+        } else {
+            $httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
+            if ($httpcode != 200 && $httpcode != 202) {
+                throw new \Exception("Unexpected HTTP code $httpcode: $response");
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Convert ActivityPub activity to ContentNation JSON format
+     *
+     * @param \mysqli $dbh database handle
+     * @param string $serviceUrl the service URL
+     * @param \Federator\Data\ActivityPub\Common\Activity $activity the activity
+     * @param string $targetUrl the target URL for the activity
+     * @return array<string, mixed>|false the json data or false on failure
+     */
+    private static function activityToJson($dbh, $serviceUrl, \Federator\Data\ActivityPub\Common\Activity $activity, string &$targetUrl)
+    {
+        $type = strtolower($activity->getType());
+        switch ($type) {
+            case 'create':
+            case 'update':
+                $object = $activity->getObject();
+                if (is_object($object)) {
+                    $objType = strtolower($object->getType());
+                    $articleId = \Federator\DIO\Posts::getOriginalArticleId($dbh, $activity);
+                    if ($articleId === null) {
+                        error_log("ContentNation::activityToJson Failed to get original article ID for create/update activity");
+                    }
+                    switch ($objType) {
+                        case 'article':
+                            // We don't support article create/update at this point in time
+                            error_log("ContentNation::activityToJson Unsupported create/update object type: {$objType}");
+                            break;
+                        case 'note':
+                            $targetUrl = $serviceUrl . '/api/article/' . $articleId . '/comment';
+                            $type = 'comment';
+                            $inReplyTo = $object->getInReplyTo();
+                            if ($inReplyTo !== '') {
+                                $target = $inReplyTo;
+                            } else {
+                                $target = $object->getObject();
+                            }
+                            $comment = null;
+                            if (is_string($target)) {
+                                if (strpos($target, '#') !== false) {
+                                    $parts = explode('#', $target);
+                                    if (count($parts) > 0) {
+                                        $comment = $parts[count($parts) - 1];
+                                    }
+                                }
+                            } else {
+                                error_log("ContentNation::activityToJson Unsupported target type for comment with id: " . $activity->getID() . " Type: " . gettype($target));
+                                return false;
+                            }
+                            return [
+                                'type' => $type,
+                                'id' => $activity->getID(),
+                                'parent' => $comment,
+                                'subject' => $object->getSummary(),
+                                'comment' => $object->getContent(),
+                            ];
+                        default:
+                            error_log("ContentNation::activityToJson Unsupported create/update object type: {$objType}");
+                            return false;
+                    }
+                }
+                break;
+
+            case 'like':
+            case 'dislike':
+                $articleId = \Federator\DIO\Posts::getOriginalArticleId($dbh, $activity);
+                if ($articleId === null) {
+                    error_log("ContentNation::activityToJson Failed to get original article ID for vote activity");
+                }
+                $voteValue = $type === 'like' ? true : false;
+                $activityType = 'vote';
+                $inReplyTo = $activity->getInReplyTo();
+                if ($inReplyTo !== '') {
+                    $target = $inReplyTo;
+                } else {
+                    $target = $activity->getObject();
+                }
+                $comment = null;
+                if (is_string($target)) {
+                    if (strpos($target, '#') !== false) {
+                        $parts = explode('#', $target);
+                        if (count($parts) > 0) {
+                            $comment = $parts[count($parts) - 1];
+                        }
+                    }
+                } else {
+                    error_log("ContentNation::activityToJson Unsupported target type for vote with id: " . $activity->getID() . " Type: " . gettype($target));
+                    return false;
+                }
+                $targetUrl = $serviceUrl . '/api/article/' . $articleId . '/vote';
+                return [
+                    'vote' => $voteValue,
+                    'type' => $activityType,
+                    'id' => $activity->getID(),
+                    'comment' => $comment,
+                ];
+
+            case 'undo':
+                $object = $activity->getObject();
+                if (is_object($object)) {
+                    $objType = strtolower($object->getType());
+                    switch ($objType) {
+                        case 'like':
+                        case 'dislike':
+                            $articleId = \Federator\DIO\Posts::getOriginalArticleId($dbh, $activity);
+                            if ($articleId === null) {
+                                error_log("ContentNation::activityToJson Failed to get original article ID for undo vote activity");
+                            }
+                            $activityType = 'vote';
+                            $inReplyTo = $object->getInReplyTo();
+                            if ($inReplyTo !== '') {
+                                $target = $inReplyTo;
+                            } else {
+                                $target = $object->getObject();
+                            }
+                            $comment = null;
+                            if (is_string($target)) {
+                                if (strpos($target, '#') !== false) {
+                                    $parts = explode('#', $target);
+                                    if (count($parts) > 0) {
+                                        $comment = $parts[count($parts) - 1];
+                                    }
+                                }
+                            } else {
+                                error_log("ContentNation::activityToJson Unsupported target type for undo vote with id: " . $activity->getID() . " Type: " . gettype($target));
+                                return false;
+                            }
+                            $targetUrl = $serviceUrl . '/api/article/' . $articleId . '/vote';
+                            return [
+                                'vote' => null,
+                                'type' => $activityType,
+                                'id' => $object->getID(),
+                                'comment' => $comment,
+                            ];
+                        case 'note':
+                            // We don't support comment deletions at this point in time
+                            error_log("ContentNation::activityToJson Unsupported undo object type: {$objType}");
+                            break;
+                        default:
+                            error_log("ContentNation::activityToJson Unsupported create/update object type: {$objType}");
+                            return false;
+                    }
+                }
+                break;
+            default:
+                error_log("ContentNation::activityToJson Unsupported activity type: {$type}");
+                return false;
+        }
+
+        return false;
+    }
+
     /**
      * check if the headers include a valid signature
      *
diff --git a/plugins/federator/dummyconnector.php b/plugins/federator/dummyconnector.php
index 4b9b62d..d4ecb8f 100644
--- a/plugins/federator/dummyconnector.php
+++ b/plugins/federator/dummyconnector.php
@@ -73,9 +73,11 @@ class DummyConnector implements Connector
      * Convert jsonData to Activity format
      *
      * @param array<string, mixed> $jsonData the json data from our platfrom @unused-param
+     * @param string $articleId the original id of the article (if applicable)
+     *                           (used to identify the article in the remote system) @unused-param
      * @return \Federator\Data\ActivityPub\Common\Activity|false
      */
-    public function jsonToActivity(array $jsonData) {
+    public function jsonToActivity(array $jsonData, &$articleId) {
         return false;
     }
 
@@ -108,6 +110,18 @@ class DummyConnector implements Connector
         return $user;
     }
 
+    /**
+     * send target-friendly json from ActivityPub activity
+     *
+     * @param \Federator\Data\FedUser $sender the user of the sender @unused-param
+     * @param \Federator\Data\ActivityPub\Common\Activity $activity the activity @unused-param
+     * @return boolean did we successfully send the activity?
+     */
+    public function sendActivity($sender, $activity)
+    {
+        return false;
+    }
+
     /**
      * check if the headers include a valid signature
      *
diff --git a/plugins/federator/rediscache.php b/plugins/federator/rediscache.php
index 6b1019c..bc3cf16 100644
--- a/plugins/federator/rediscache.php
+++ b/plugins/federator/rediscache.php
@@ -125,9 +125,11 @@ class RedisCache implements Cache
      * Convert jsonData to Activity format
      *
      * @param array<string, mixed> $jsonData the json data from our platfrom @unused-param
+     * @param string $articleId the original id of the article (if applicable)
+     *                           (used to identify the article in the remote system) @unused-param
      * @return \Federator\Data\ActivityPub\Common\Activity|false
      */
-    public function jsonToActivity(array $jsonData)
+    public function jsonToActivity(array $jsonData, &$articleId)
     {
         error_log("rediscache::jsonToActivity not implemented");
         return false;
@@ -353,6 +355,18 @@ class RedisCache implements Cache
         $this->redis->setEx($key, $this->publicKeyPemTTL, $publicKeyPem);
     }
 
+    /**
+     * send target-friendly json from ActivityPub activity
+     *
+     * @param \Federator\Data\FedUser $sender the user of the sender @unused-param
+     * @param \Federator\Data\ActivityPub\Common\Activity $activity the activity @unused-param
+     * @return boolean did we successfully send the activity?
+     */
+    public function sendActivity($sender, $activity)
+    {
+        return false;
+    }
+
     /**
      * check if the headers include a valid signature
      *
diff --git a/sql/2025-05-27.sql b/sql/2025-05-27.sql
new file mode 100644
index 0000000..0cc7654
--- /dev/null
+++ b/sql/2025-05-27.sql
@@ -0,0 +1,2 @@
+alter table posts add `article_id` varchar(255) null default null comment 'The optional original article id (of non-federated system, e.g. CN)';
+update settings set `value`="2025-05-27" where `key`="database_version";