diff --git a/src/Model/APContact.php b/src/Model/APContact.php
index 0a9d45f35..d0a0d0d3f 100644
--- a/src/Model/APContact.php
+++ b/src/Model/APContact.php
@@ -28,6 +28,7 @@ use Friendica\Core\System;
 use Friendica\Database\DBA;
 use Friendica\Database\DBStructure;
 use Friendica\DI;
+use Friendica\Network\HTTPException;
 use Friendica\Network\Probe;
 use Friendica\Protocol\ActivityNamespace;
 use Friendica\Protocol\ActivityPub;
@@ -178,8 +179,12 @@ class APContact
 		}
 
 		if (Network::isLocalLink($url) && ($local_uid = User::getIdForURL($url))) {
-			$data  = Transmitter::getProfile($local_uid);
-			$local_owner = User::getOwnerDataById($local_uid);
+			try {
+				$data = Transmitter::getProfile($local_uid);
+				$local_owner = User::getOwnerDataById($local_uid);
+			} catch(HTTPException\NotFoundException $e) {
+				$data = null;
+			}
 		}
 
 		if (empty($data)) {
diff --git a/src/Module/Friendica.php b/src/Module/Friendica.php
index 5e77eb00f..95a319a41 100644
--- a/src/Module/Friendica.php
+++ b/src/Module/Friendica.php
@@ -29,6 +29,7 @@ use Friendica\Core\System;
 use Friendica\Database\PostUpdate;
 use Friendica\DI;
 use Friendica\Model\User;
+use Friendica\Network\HTTPException;
 use Friendica\Protocol\ActivityPub;
 
 /**
@@ -112,11 +113,13 @@ class Friendica extends BaseModule
 	public static function rawContent(array $parameters = [])
 	{
 		if (ActivityPub::isRequest()) {
-			$data = ActivityPub\Transmitter::getProfile(0);
-			if (!empty($data)) {
+			try {
+				$data = ActivityPub\Transmitter::getProfile(0);
 				header('Access-Control-Allow-Origin: *');
 				header('Cache-Control: max-age=23200, stale-while-revalidate=23200');
 				System::jsonExit($data, 'application/activity+json');
+			} catch (HTTPException\NotFoundException $e) {
+				System::jsonError(404, ['error' => 'Record not found']);
 			}
 		}
 
diff --git a/src/Module/Profile/Profile.php b/src/Module/Profile/Profile.php
index 4f083db26..a4fc69685 100644
--- a/src/Module/Profile/Profile.php
+++ b/src/Module/Profile/Profile.php
@@ -52,12 +52,13 @@ class Profile extends BaseProfile
 		if (ActivityPub::isRequest()) {
 			$user = DBA::selectFirst('user', ['uid'], ['nickname' => $parameters['nickname']]);
 			if (DBA::isResult($user)) {
-				// The function returns an empty array when the account is removed, expired or blocked
-				$data = ActivityPub\Transmitter::getProfile($user['uid']);
-				if (!empty($data)) {
+				try {
+					$data = ActivityPub\Transmitter::getProfile($user['uid']);
 					header('Access-Control-Allow-Origin: *');
 					header('Cache-Control: max-age=23200, stale-while-revalidate=23200');
 					System::jsonExit($data, 'application/activity+json');
+				} catch (HTTPException\NotFoundException $e) {
+					System::jsonError(404, ['error' => 'Record not found']);
 				}
 			}
 
diff --git a/src/Network/Probe.php b/src/Network/Probe.php
index 9ee338e8f..d0aaaa7a0 100644
--- a/src/Network/Probe.php
+++ b/src/Network/Probe.php
@@ -23,6 +23,7 @@ namespace Friendica\Network;
 
 use DOMDocument;
 use DomXPath;
+use Exception;
 use Friendica\Core\Hook;
 use Friendica\Core\Logger;
 use Friendica\Core\Protocol;
@@ -2198,10 +2199,17 @@ class Probe
 	 *
 	 * @param string $url
 	 * @return array probed data
+	 * @throws HTTPException\InternalServerErrorException
+	 * @throws HTTPException\NotFoundException
 	 */
-	private static function localProbe(string $url)
+	private static function localProbe(string $url): array
 	{
-		if ($uid = User::getIdForURL($url)) {
+		try {
+			$uid = User::getIdForURL($url);
+			if (!$uid) {
+				throw new HTTPException\NotFoundException('User not found.');
+			}
+
 			$profile   = User::getOwnerDataById($uid);
 			$approfile = ActivityPub\Transmitter::getProfile($uid);
 
@@ -2209,25 +2217,30 @@ class Probe
 				$profile['gsid'] = GServer::getID($approfile['generator']['url']);
 			}
 
-			$data = ['name' => $profile['name'], 'nick' => $profile['nick'], 'guid' => $approfile['diaspora:guid'] ?? '',
+			$data = [
+				'name' => $profile['name'], 'nick' => $profile['nick'], 'guid' => $approfile['diaspora:guid'] ?? '',
 				'url' => $profile['url'], 'addr' => $profile['addr'], 'alias' => $profile['alias'],
 				'photo' => Contact::getAvatarUrlForId($profile['id'], $profile['updated']),
 				'header' => $profile['header'] ? Contact::getHeaderUrlForId($profile['id'], $profile['updated']) : '',
 				'account-type' => $profile['contact-type'], 'community' => ($profile['contact-type'] == User::ACCOUNT_TYPE_COMMUNITY),
-				'keywords' => $profile['keywords'], 'location' => $profile['location'], 'about' => $profile['about'], 
+				'keywords' => $profile['keywords'], 'location' => $profile['location'], 'about' => $profile['about'],
 				'hide' => !$profile['net-publish'], 'batch' => '', 'notify' => $profile['notify'],
 				'poll' => $profile['poll'], 'request' => $profile['request'], 'confirm' => $profile['confirm'],
-				'subscribe' => $approfile['generator']['url'] . '/follow?url={uri}', 'poco' => $profile['poco'], 
+				'subscribe' => $approfile['generator']['url'] . '/follow?url={uri}', 'poco' => $profile['poco'],
 				'following' => $approfile['following'], 'followers' => $approfile['followers'],
 				'inbox' => $approfile['inbox'], 'outbox' => $approfile['outbox'],
-				'sharedinbox' => $approfile['endpoints']['sharedInbox'], 'network' => Protocol::DFRN, 
+				'sharedinbox' => $approfile['endpoints']['sharedInbox'], 'network' => Protocol::DFRN,
 				'pubkey' => $profile['upubkey'], 'baseurl' => $approfile['generator']['url'], 'gsid' => $profile['gsid'],
-				'manually-approve' => in_array($profile['page-flags'], [User::PAGE_FLAGS_NORMAL, User::PAGE_FLAGS_PRVGROUP])];
-		} else {
+				'manually-approve' => in_array($profile['page-flags'], [User::PAGE_FLAGS_NORMAL, User::PAGE_FLAGS_PRVGROUP])
+			];
+		} catch (Exception $e) {
 			// Default values for non existing targets
-			$data = ['name' => $url, 'nick' => $url, 'url' => $url, 'network' => Protocol::PHANTOM,
-				'photo' => DI::baseUrl() . Contact::DEFAULT_AVATAR_PHOTO];
+			$data = [
+				'name' => $url, 'nick' => $url, 'url' => $url, 'network' => Protocol::PHANTOM,
+				'photo' => DI::baseUrl() . Contact::DEFAULT_AVATAR_PHOTO
+			];
 		}
-		return self::rearrangeData($data);		
+
+		return self::rearrangeData($data);
 	}
 }
diff --git a/src/Protocol/ActivityPub/Transmitter.php b/src/Protocol/ActivityPub/Transmitter.php
index 20b8f2a26..6c78db302 100644
--- a/src/Protocol/ActivityPub/Transmitter.php
+++ b/src/Protocol/ActivityPub/Transmitter.php
@@ -23,7 +23,6 @@ namespace Friendica\Protocol\ActivityPub;
 
 use Friendica\Content\Feature;
 use Friendica\Content\Text\BBCode;
-use Friendica\Content\Text\Plaintext;
 use Friendica\Core\Cache\Duration;
 use Friendica\Core\Logger;
 use Friendica\Core\Protocol;
@@ -35,12 +34,12 @@ use Friendica\Model\Contact;
 use Friendica\Model\Conversation;
 use Friendica\Model\GServer;
 use Friendica\Model\Item;
-use Friendica\Model\ItemURI;
-use Friendica\Model\Profile;
 use Friendica\Model\Photo;
 use Friendica\Model\Post;
+use Friendica\Model\Profile;
 use Friendica\Model\Tag;
 use Friendica\Model\User;
+use Friendica\Network\HTTPException;
 use Friendica\Protocol\Activity;
 use Friendica\Protocol\ActivityPub;
 use Friendica\Protocol\Relay;
@@ -310,13 +309,18 @@ class Transmitter
 	/**
 	 * Return the ActivityPub profile of the given user
 	 *
-	 * @param integer $uid User ID
+	 * @param int $uid User ID
 	 * @return array with profile data
-	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+	 * @throws HTTPException\NotFoundException
+	 * @throws HTTPException\InternalServerErrorException
 	 */
-	public static function getProfile($uid)
+	public static function getProfile(int $uid): array
 	{
 		$owner = User::getOwnerDataById($uid);
+		if (!isset($owner['id'])) {
+			DI::logger()->error('Unable to find owner data for uid', ['uid' => $uid, 'callstack' => System::callstack(20)]);
+			throw new HTTPException\NotFoundException('User not found.');
+		}
 
 		$data = ['@context' => ActivityPub::CONTEXT];
 		$data['id'] = $owner['url'];
@@ -1855,10 +1859,11 @@ class Transmitter
 	 * @param string  $inbox Target inbox
 	 *
 	 * @return boolean was the transmission successful?
-	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+	 * @throws HTTPException\InternalServerErrorException
+	 * @throws HTTPException\NotFoundException
 	 * @throws \ImagickException
 	 */
-	public static function sendProfileUpdate($uid, $inbox)
+	public static function sendProfileUpdate(int $uid, string $inbox): bool
 	{
 		$owner = User::getOwnerDataById($uid);
 		$profile = APContact::getByURL($owner['url']);