diff --git a/includes/activitypub/class-handler.php b/includes/activitypub/class-handler.php
new file mode 100644
index 0000000..b9961d2
--- /dev/null
+++ b/includes/activitypub/class-handler.php
@@ -0,0 +1,36 @@
+<?php
+/**
+ * Class responsible for registering handlers for incoming activities to the ActivityPub plugin.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
+ * @license AGPL-3.0-or-later
+ */
+
+namespace Event_Bridge_For_ActivityPub\ActivityPub;
+
+// Exit if accessed directly.
+defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore
+
+use Event_Bridge_For_ActivityPub\ActivityPub\Handler\Accept;
+use Event_Bridge_For_ActivityPub\ActivityPub\Handler\Announce;
+use Event_Bridge_For_ActivityPub\ActivityPub\Handler\Update;
+use Event_Bridge_For_ActivityPub\ActivityPub\Handler\Create;
+use Event_Bridge_For_ActivityPub\ActivityPub\Handler\Delete;
+
+/**
+ *  Class responsible for registering handlers for incoming activities to the ActivityPub plugin.
+ */
+class Handler {
+	/**
+	 * Register all ActivityPub handlers.
+	 */
+	public static function register_handlers() {
+
+		Accept::init();
+		Announce::init();
+		Update::init();
+		Create::init();
+		Delete::init();
+	}
+}
diff --git a/includes/activitypub/collection/class-event-sources.php b/includes/activitypub/collection/class-event-sources.php
index 6703804..314bb73 100644
--- a/includes/activitypub/collection/class-event-sources.php
+++ b/includes/activitypub/collection/class-event-sources.php
@@ -3,6 +3,7 @@
  * Event sources collection file.
  *
  * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
  * @license AGPL-3.0-or-later
  */
 
@@ -87,8 +88,8 @@ class Event_Sources {
 			self::POST_TYPE,
 			'event_source_active',
 			array(
-				'type'              => 'bool',
-				'single'            => true,
+				'type'   => 'bool',
+				'single' => true,
 			)
 		);
 
@@ -294,7 +295,7 @@ class Event_Sources {
 
 		$actor = Event_Source::init_from_cpt( get_post( $post_id ) );
 
-		if ( is_wp_error( $actor ) ) {
+		if ( ! $actor instanceof Event_Source ) {
 			return $actor;
 		}
 
@@ -309,7 +310,7 @@ class Event_Sources {
 		$activity->set_cc( null );
 		$activity->set_actor( $application->get_id() );
 		$activity->set_object( $to );
-		$activity->set_id( $actor . '#follow-' . \preg_replace( '~^https?://~', '', $to ) );
+		$activity->set_id( $application->get_id() . '#follow-' . \preg_replace( '~^https?://~', '', $to ) );
 		$activity = $activity->to_json();
 		\Activitypub\safe_remote_post( $inbox, $activity, \Activitypub\Collection\Actors::APPLICATION_USER_ID );
 	}
@@ -345,7 +346,7 @@ class Event_Sources {
 
 		$actor = Event_Source::init_from_cpt( get_post( $post_id ) );
 
-		if ( is_wp_error( $actor ) ) {
+		if ( ! $actor instanceof Event_Source ) {
 			return $actor;
 		}
 
diff --git a/includes/activitypub/handler/class-accept.php b/includes/activitypub/handler/class-accept.php
new file mode 100644
index 0000000..4a86ae5
--- /dev/null
+++ b/includes/activitypub/handler/class-accept.php
@@ -0,0 +1,50 @@
+<?php
+/**
+ * Accept handler file.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
+ * @license AGPL-3.0-or-later */
+
+namespace Event_Bridge_For_ActivityPub\ActivityPub\Handler;
+
+use Activitypub\Notification;
+use Activitypub\Collection\Actors;
+
+/**
+ * Handle Accept requests.
+ */
+class Accept {
+	/**
+	 * Initialize the class, registering WordPress hooks.
+	 */
+	public static function init() {
+		\add_action(
+			'activitypub_inbox_accept',
+			array( self::class, 'handle_accept' )
+		);
+	}
+
+	/**
+	 * Handle "Follow" requests.
+	 *
+	 * @param array $activity The activity object.
+	 */
+	public static function handle_accept( $activity ) {
+		if ( ! isset( $activity['object'] ) ) {
+			return;
+		}
+
+		$object = Actors::get_by_resource( $activity['object'] );
+
+		if ( ! $object || is_wp_error( $object ) ) {
+			// If we can not find a actor, we handle the `Accept` activity.
+			return;
+		}
+
+		// We only expect `Accept` activities being answers to follow requests by the application actor.
+		if ( Actors::APPLICATION_USER_ID !== $object->get__id() ) {
+			return;
+		}
+	}
+}
diff --git a/includes/activitypub/handler/class-announce.php b/includes/activitypub/handler/class-announce.php
new file mode 100644
index 0000000..f79b3e7
--- /dev/null
+++ b/includes/activitypub/handler/class-announce.php
@@ -0,0 +1,49 @@
+<?php
+/**
+ * Accept handler file.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ */
+
+namespace Event_Bridge_For_ActivityPub\ActivityPub\Handler;
+
+use Activitypub\Notification;
+use Activitypub\Collection\Actors;
+
+/**
+ * Handle Accept requests.
+ */
+class Announce {
+	/**
+	 * Initialize the class, registering WordPress hooks.
+	 */
+	public static function init() {
+		\add_action(
+			'activitypub_inbox_announce',
+			array( self::class, 'handle_announce' )
+		);
+	}
+
+	/**
+	 * Handle "Announce" requests.
+	 *
+	 * @param array $activity The activity object.
+	 */
+	public static function handle_announce( $activity ) {
+		if ( ! isset( $activity['object'] ) ) {
+			return;
+		}
+
+		$object = Actors::get_by_resource( $activity['object'] );
+
+		if ( ! $object || is_wp_error( $object ) ) {
+			// If we can not find a actor, we handle the `Accept` activity.
+			return;
+		}
+
+		// We only expect `Accept` activities being answers to follow requests by the application actor.
+		if ( Actors::APPLICATION_USER_ID !== $object->get__id() ) {
+			return;
+		}
+	}
+}
diff --git a/includes/activitypub/handler/class-create.php b/includes/activitypub/handler/class-create.php
new file mode 100644
index 0000000..854a084
--- /dev/null
+++ b/includes/activitypub/handler/class-create.php
@@ -0,0 +1,49 @@
+<?php
+/**
+ * Create handler file.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ */
+
+namespace Event_Bridge_For_ActivityPub\ActivityPub\Handler;
+
+use Activitypub\Notification;
+use Activitypub\Collection\Actors;
+
+/**
+ * Handle Create requests.
+ */
+class Create {
+	/**
+	 * Initialize the class, registering WordPress hooks.
+	 */
+	public static function init() {
+		\add_action(
+			'activitypub_inbox_create',
+			array( self::class, 'handle_create' )
+		);
+	}
+
+	/**
+	 * Handle "Create" requests.
+	 *
+	 * @param array $activity The activity object.
+	 */
+	public static function handle_create( $activity ) {
+		if ( ! isset( $activity['object'] ) ) {
+			return;
+		}
+
+		$object = Actors::get_by_resource( $activity['object'] );
+
+		if ( ! $object || is_wp_error( $object ) ) {
+			// If we can not find a actor, we handle the `create` activity.
+			return;
+		}
+
+		// We only expect `create` activities being answers to follow requests by the application actor.
+		if ( Actors::APPLICATION_USER_ID !== $object->get__id() ) {
+			return;
+		}
+	}
+}
diff --git a/includes/activitypub/handler/class-delete.php b/includes/activitypub/handler/class-delete.php
new file mode 100644
index 0000000..ff4cede
--- /dev/null
+++ b/includes/activitypub/handler/class-delete.php
@@ -0,0 +1,49 @@
+<?php
+/**
+ * Delete handler file.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ */
+
+namespace Event_Bridge_For_ActivityPub\ActivityPub\Handler;
+
+use Activitypub\Notification;
+use Activitypub\Collection\Actors;
+
+/**
+ * Handle Delete requests.
+ */
+class Delete {
+	/**
+	 * Initialize the class, registering WordPress hooks.
+	 */
+	public static function init() {
+		\add_action(
+			'activitypub_inbox_delete',
+			array( self::class, 'handle_delete' )
+		);
+	}
+
+	/**
+	 * Handle "Follow" requests.
+	 *
+	 * @param array $activity The activity object.
+	 */
+	public static function handle_delete( $activity ) {
+		if ( ! isset( $activity['object'] ) ) {
+			return;
+		}
+
+		$object = Actors::get_by_resource( $activity['object'] );
+
+		if ( ! $object || is_wp_error( $object ) ) {
+			// If we can not find a actor, we handle the `Delete` activity.
+			return;
+		}
+
+		// We only expect `Delete` activities being answers to follow requests by the application actor.
+		if ( Actors::APPLICATION_USER_ID !== $object->get__id() ) {
+			return;
+		}
+	}
+}
diff --git a/includes/activitypub/handler/class-update.php b/includes/activitypub/handler/class-update.php
new file mode 100644
index 0000000..16b7559
--- /dev/null
+++ b/includes/activitypub/handler/class-update.php
@@ -0,0 +1,49 @@
+<?php
+/**
+ * Update handler file.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ */
+
+namespace Event_Bridge_For_ActivityPub\ActivityPub\Handler;
+
+use Activitypub\Notification;
+use Activitypub\Collection\Actors;
+
+/**
+ * Handle Update requests.
+ */
+class Update {
+	/**
+	 * Initialize the class, registering WordPress hooks.
+	 */
+	public static function init() {
+		\add_action(
+			'activitypub_inbox_update',
+			array( self::class, 'handle_update' )
+		);
+	}
+
+	/**
+	 * Handle "Follow" requests.
+	 *
+	 * @param array $activity The activity object.
+	 */
+	public static function handle_update( $activity ) {
+		if ( ! isset( $activity['object'] ) ) {
+			return;
+		}
+
+		$object = Actors::get_by_resource( $activity['object'] );
+
+		if ( ! $object || is_wp_error( $object ) ) {
+			// If we can not find a actor, we handle the `Update` activity.
+			return;
+		}
+
+		// We only expect `Update` activities being answers to follow requests by the application actor.
+		if ( Actors::APPLICATION_USER_ID !== $object->get__id() ) {
+			return;
+		}
+	}
+}
diff --git a/includes/admin/class-settings-page.php b/includes/admin/class-settings-page.php
index a81252f..c49602b 100644
--- a/includes/admin/class-settings-page.php
+++ b/includes/admin/class-settings-page.php
@@ -77,19 +77,17 @@ class Settings_Page {
 
 		if ( isset( $url['path'] ) && isset( $url['host'] ) && isset( $url['scheme'] ) ) {
 			$actor_url = $event_source;
+		} elseif ( preg_match( '/^@?' . Event_Source::ACTIVITYPUB_USER_HANDLE_REGEXP . '$/i', $event_source ) ) {
+			$actor_url = Webfinger::resolve( $event_source );
+			if ( is_wp_error( $actor_url ) ) {
+				return;
+			}
 		} else {
-			if ( preg_match( '/^@?' . Event_Source::ACTIVITYPUB_USER_HANDLE_REGEXP . '$/i', $event_source ) ) {
-				$actor_url = Webfinger::resolve( $event_source );
-				if ( is_wp_error( $actor_url ) ) {
-					return;
-				}
-			} else {
-				if ( ! isset( $url['path'] ) && isset( $url['host'] ) ) {
-					$actor_url = Event_Sources::get_application_actor( $url['host'] );
-				}
-				if ( self::is_domain( $event_source ) ) {
-					$actor_url = Event_Sources::get_application_actor( $event_source );
-				}
+			if ( ! isset( $url['path'] ) && isset( $url['host'] ) ) {
+				$actor_url = Event_Sources::get_application_actor( $url['host'] );
+			}
+			if ( self::is_domain( $event_source ) ) {
+				$actor_url = Event_Sources::get_application_actor( $event_source );
 			}
 		}
 
diff --git a/includes/class-event-sources.php b/includes/class-event-sources.php
index b636569..f2701fa 100644
--- a/includes/class-event-sources.php
+++ b/includes/class-event-sources.php
@@ -3,6 +3,8 @@
  * Class for handling and saving the ActivityPub event sources (i.e. follows).
  *
  * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
+ * @license AGPL-3.0-or-later
  */
 
 namespace Event_Bridge_For_ActivityPub;
diff --git a/includes/class-setup.php b/includes/class-setup.php
index df9970a..e18e468 100644
--- a/includes/class-setup.php
+++ b/includes/class-setup.php
@@ -15,12 +15,13 @@ namespace Event_Bridge_For_ActivityPub;
 // Exit if accessed directly.
 defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore
 
+use Event_Bridge_For_ActivityPub\ActivityPub\Collection\Event_Sources as Event_Sources_Collection;
+use Event_Bridge_For_ActivityPub\ActivityPub\Handler;
 use Event_Bridge_For_ActivityPub\Admin\Event_Plugin_Admin_Notices;
 use Event_Bridge_For_ActivityPub\Admin\General_Admin_Notices;
 use Event_Bridge_For_ActivityPub\Admin\Health_Check;
 use Event_Bridge_For_ActivityPub\Admin\Settings_Page;
 use Event_Bridge_For_ActivityPub\Integrations\Event_Plugin;
-use Event_Bridge_For_ActivityPub\ActivityPub\Collection\Event_Sources as Event_Sources_Collection;
 
 require_once ABSPATH . 'wp-admin/includes/plugin.php';
 
@@ -178,6 +179,8 @@ class Setup {
 			array( Settings_Page::class, 'settings_link' )
 		);
 
+		add_action( 'activitypub_register_handlers', array( Handler::class, 'register_activitypub_handlers' ) ) ;
+
 		// If we don't have any active event plugins, or the ActivityPub plugin is not enabled, abort here.
 		if ( empty( $this->active_event_plugins ) || ! $this->activitypub_plugin_is_active ) {
 			return;
diff --git a/includes/integrations/class-event-plugin.php b/includes/integrations/class-event-plugin.php
index 56d020a..aba3d22 100644
--- a/includes/integrations/class-event-plugin.php
+++ b/includes/integrations/class-event-plugin.php
@@ -6,6 +6,7 @@
  *
  * @package Event_Bridge_For_ActivityPub
  * @since 1.0.0
+ * @license AGPL-3.0-or-later
  */
 
 namespace Event_Bridge_For_ActivityPub\Integrations;
diff --git a/includes/table/class-event-sources.php b/includes/table/class-event-sources.php
index 2969483..9dcbf03 100644
--- a/includes/table/class-event-sources.php
+++ b/includes/table/class-event-sources.php
@@ -3,6 +3,8 @@
  * Event Sources Table-Class file.
  *
  * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
+ * @license AGPL-3.0-or-later
  */
 
 namespace Event_Bridge_For_ActivityPub\Table;
@@ -40,13 +42,13 @@ class Event_Sources extends WP_List_Table {
 	 */
 	public function get_columns() {
 		return array(
-			'cb'         => '<input type="checkbox" />',
-			'icon'       => \__( 'Icon', 'event-bridge-for-activitypub' ),
-			'name'       => \__( 'Name', 'event-bridge-for-activitypub' ),
-			'active'     => \__( 'Active', 'event-bridge-for-activitypub' ),
-			'url'        => \__( 'URL', 'event-bridge-for-activitypub' ),
-			'published'  => \__( 'Followed', 'event-bridge-for-activitypub' ),
-			'modified'   => \__( 'Last updated', 'event-bridge-for-activitypub' ),
+			'cb'        => '<input type="checkbox" />',
+			'icon'      => \__( 'Icon', 'event-bridge-for-activitypub' ),
+			'name'      => \__( 'Name', 'event-bridge-for-activitypub' ),
+			'active'    => \__( 'Active', 'event-bridge-for-activitypub' ),
+			'url'       => \__( 'URL', 'event-bridge-for-activitypub' ),
+			'published' => \__( 'Followed', 'event-bridge-for-activitypub' ),
+			'modified'  => \__( 'Last updated', 'event-bridge-for-activitypub' ),
 		);
 	}
 
@@ -57,9 +59,9 @@ class Event_Sources extends WP_List_Table {
 	 */
 	public function get_sortable_columns() {
 		return array(
-			'name' => array( 'name', true ),
-			'modified'   => array( 'modified', false ),
-			'published'  => array( 'published', false ),
+			'name'      => array( 'name', true ),
+			'modified'  => array( 'modified', false ),
+			'published' => array( 'published', false ),
 		);
 	}
 
@@ -113,7 +115,7 @@ class Event_Sources extends WP_List_Table {
 				'icon'       => esc_attr( $actor->get_icon_url() ),
 				'name'       => esc_attr( $actor->get_name() ),
 				'url'        => esc_attr( object_to_uri( $actor->get_id() ) ),
-				'active'     => esc_attr( get_post_meta( $actor->get__id(), 'event_source_active', true) ),
+				'active'     => esc_attr( get_post_meta( $actor->get__id(), 'event_source_active', true ) ),
 				'identifier' => esc_attr( $actor->get_id() ),
 				'published'  => esc_attr( $actor->get_published() ),
 				'modified'   => esc_attr( $actor->get_updated() ),
diff --git a/templates/event-sources.php b/templates/event-sources.php
index b2a4b20..47e2f22 100644
--- a/templates/event-sources.php
+++ b/templates/event-sources.php
@@ -3,6 +3,8 @@
  * Event Sources management page for the ActivityPub Event Bridge.
  *
  * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
+ * @license AGPL-3.0-or-later
  */
 
 // Exit if accessed directly.