diff --git a/mod/events.php b/mod/events.php
index 8e9606b203..86cec9a7d4 100644
--- a/mod/events.php
+++ b/mod/events.php
@@ -21,6 +21,7 @@ use Friendica\Module\Login;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Strings;
 use Friendica\Util\Temporal;
+use Friendica\Worker\Delivery;
 
 function events_init(App $a)
 {
@@ -195,7 +196,7 @@ function events_post(App $a)
 	$item_id = Event::store($datarray);
 
 	if (!$cid) {
-		Worker::add(PRIORITY_HIGH, "Notifier", "event", $item_id);
+		Worker::add(PRIORITY_HIGH, "Notifier", Delivery::POST, $item_id);
 	}
 
 	$a->internalRedirect('events');
diff --git a/mod/fsuggest.php b/mod/fsuggest.php
index 2cede56852..2bddf48133 100644
--- a/mod/fsuggest.php
+++ b/mod/fsuggest.php
@@ -10,6 +10,7 @@ use Friendica\Core\Worker;
 use Friendica\Database\DBA;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Strings;
+use Friendica\Worker\Delivery;
 
 function fsuggest_post(App $a)
 {
@@ -51,7 +52,7 @@ function fsuggest_post(App $a)
 		'photo' => $contact['avatar'], 'note' => $note, 'created' => DateTimeFormat::utcNow()];
 	DBA::insert('fsuggest', $fields);
 
-	Worker::add(PRIORITY_HIGH, 'Notifier', 'suggest', DBA::lastInsertId());
+	Worker::add(PRIORITY_HIGH, 'Notifier', Delivery::SUGGESTION, DBA::lastInsertId());
 
 	info(L10n::t('Friend suggestion sent.') . EOL);
 }
diff --git a/mod/item.php b/mod/item.php
index 1fccbca4d6..20dc9dfdae 100644
--- a/mod/item.php
+++ b/mod/item.php
@@ -604,8 +604,6 @@ function item_post(App $a) {
 		$origin = $_REQUEST['origin'];
 	}
 
-	$notify_type = ($toplevel_item_id ? Delivery::COMMENT : Delivery::POST);
-
 	$uri = ($message_id ? $message_id : Item::newURI($api_source ? $profile_uid : $uid, $guid));
 
 	// Fallback so that we alway have a parent uri
@@ -870,7 +868,7 @@ function item_post(App $a) {
 	// When we are doing some forum posting via ! we have to start the notifier manually.
 	// These kind of posts don't initiate the notifier call in the item class.
 	if ($only_to_forum) {
-		Worker::add(PRIORITY_HIGH, "Notifier", $notify_type, $post_id);
+		Worker::add(PRIORITY_HIGH, "Notifier", Delivery::POST, $post_id);
 	}
 
 	Logger::log('post_complete');
diff --git a/mod/settings.php b/mod/settings.php
index 45f11cdb6c..ab7586733a 100644
--- a/mod/settings.php
+++ b/mod/settings.php
@@ -27,6 +27,7 @@ use Friendica\Protocol\Email;
 use Friendica\Util\Network;
 use Friendica\Util\Strings;
 use Friendica\Util\Temporal;
+use Friendica\Worker\Delivery;
 
 function get_theme_config_file($theme)
 {
@@ -389,7 +390,7 @@ function settings_post(App $a)
 	BaseModule::checkFormSecurityTokenRedirectOnError('/settings', 'settings');
 
 	if (!empty($_POST['resend_relocate'])) {
-		Worker::add(PRIORITY_HIGH, 'Notifier', 'relocate', local_user());
+		Worker::add(PRIORITY_HIGH, 'Notifier', Delivery::RELOCATION, local_user());
 		info(L10n::t("Relocate message has been send to your contacts"));
 		$a->internalRedirect('settings');
 	}
diff --git a/mod/tagger.php b/mod/tagger.php
index 5d3d1923e4..2c15cdd28c 100644
--- a/mod/tagger.php
+++ b/mod/tagger.php
@@ -12,6 +12,7 @@ use Friendica\Database\DBA;
 use Friendica\Model\Item;
 use Friendica\Util\Strings;
 use Friendica\Util\XML;
+use Friendica\Worker\Delivery;
 
 function tagger_content(App $a) {
 
@@ -194,7 +195,7 @@ EOT;
 
 	Hook::callAll('post_local_end', $arr);
 
-	Worker::add(PRIORITY_HIGH, "Notifier", "tag", $post_id);
+	Worker::add(PRIORITY_HIGH, "Notifier", Delivery::POST, $post_id);
 
 	exit();
 }
diff --git a/src/Core/UserImport.php b/src/Core/UserImport.php
index 97a6e6028e..71767e8cef 100644
--- a/src/Core/UserImport.php
+++ b/src/Core/UserImport.php
@@ -10,6 +10,7 @@ use Friendica\Database\DBStructure;
 use Friendica\Model\Photo;
 use Friendica\Object\Image;
 use Friendica\Util\Strings;
+use Friendica\Worker\Delivery;
 
 /**
  * @brief UserImport class
@@ -278,7 +279,7 @@ class UserImport
 		}
 
 		// send relocate messages
-		Worker::add(PRIORITY_HIGH, 'Notifier', 'relocate', $newuid);
+		Worker::add(PRIORITY_HIGH, 'Notifier', Delivery::RELOCATION, $newuid);
 
 		info(L10n::t("Done. You can now login with your username and password"));
 		$a->internalRedirect('login');
diff --git a/src/Core/Worker.php b/src/Core/Worker.php
index 0f4a527f6b..d7e5479267 100644
--- a/src/Core/Worker.php
+++ b/src/Core/Worker.php
@@ -1100,7 +1100,7 @@ class Worker
 	 * @param (integer|array) priority or parameter array, strings are deprecated and are ignored
 	 *
 	 * next args are passed as $cmd command line
-	 * or: Worker::add(PRIORITY_HIGH, "Notifier", "drop", $drop_id);
+	 * or: Worker::add(PRIORITY_HIGH, "Notifier", Delivery::DELETION, $drop_id);
 	 * or: Worker::add(array('priority' => PRIORITY_HIGH, 'dont_fork' => true), "CreateShadowEntry", $post_id);
 	 *
 	 * @return boolean "false" if proc_run couldn't be executed
diff --git a/src/Model/Item.php b/src/Model/Item.php
index e57b3cbd3c..4dc1be648a 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -926,7 +926,7 @@ class Item extends BaseObject
 			// We only need to notfiy others when it is an original entry from us.
 			// Only call the notifier when the item has some content relevant change.
 			if ($item['origin'] && in_array('edited', array_keys($fields))) {
-				Worker::add(PRIORITY_HIGH, "Notifier", 'edit_post', $item['id']);
+				Worker::add(PRIORITY_HIGH, "Notifier", Delivery::POST, $item['id']);
 			}
 		}
 
@@ -1096,7 +1096,7 @@ class Item extends BaseObject
 			self::delete(['uri' => $item['uri'], 'deleted' => false], $priority);
 
 			// send the notification upstream/downstream
-			Worker::add(['priority' => $priority, 'dont_fork' => true], "Notifier", "drop", intval($item['id']));
+			Worker::add(['priority' => $priority, 'dont_fork' => true], "Notifier", Delivery::DELETION, intval($item['id']));
 		} elseif ($item['uid'] != 0) {
 
 			// When we delete just our local user copy of an item, we have to set a marker to hide it
@@ -1509,7 +1509,7 @@ class Item extends BaseObject
 
 		$item['thr-parent'] = $item['parent-uri'];
 
-		$notify_type = '';
+		$notify_type = Delivery::POST;
 		$allow_cid = '';
 		$allow_gid = '';
 		$deny_cid  = '';
@@ -1522,7 +1522,6 @@ class Item extends BaseObject
 			$allow_gid = $item['allow_gid'];
 			$deny_cid  = $item['deny_cid'];
 			$deny_gid  = $item['deny_gid'];
-			$notify_type = Delivery::POST;
 		} else {
 			// find the parent and snarf the item id and ACLs
 			// and anything else we need to inherit
@@ -1560,7 +1559,6 @@ class Item extends BaseObject
 				$deny_cid       = $parent['deny_cid'];
 				$deny_gid       = $parent['deny_gid'];
 				$item['wall']   = $parent['wall'];
-				$notify_type    = Delivery::COMMENT;
 
 				/*
 				 * If the parent is private, force privacy for the entire conversation
@@ -1882,20 +1880,8 @@ class Item extends BaseObject
 
 		check_user_notification($current_post);
 
-		if ($notify) {
+		if ($notify || ($item['visible'] && ((!empty($parent) && $parent['origin']) || $item['origin']))) {
 			Worker::add(['priority' => $priority, 'dont_fork' => true], 'Notifier', $notify_type, $current_post);
-		} elseif ($item['visible'] && ((!empty($parent) && $parent['origin']) || $item['origin'])) {
-			if ($item['gravity'] == GRAVITY_ACTIVITY) {
-				$cmd = $item['origin'] ? Delivery::ACTIVITY : 'activity-import';
-			} elseif ($item['gravity'] == GRAVITY_COMMENT) {
-				$cmd = $item['origin'] ? Delivery::COMMENT : 'comment-import';
-			} elseif (!empty($notify_type)) {
-				$cmd = $notify_type;
-			} else {
-				$cmd = Delivery::POST;
-			}
-
-			Worker::add(['priority' => $priority, 'dont_fork' => true], 'Notifier', $cmd, $current_post);
 		}
 
 		return $current_post;
@@ -2611,7 +2597,7 @@ class Item extends BaseObject
 
 		self::updateThread($item_id);
 
-		Worker::add(['priority' => PRIORITY_HIGH, 'dont_fork' => true], 'Notifier', 'tgroup', $item_id);
+		Worker::add(['priority' => PRIORITY_HIGH, 'dont_fork' => true], 'Notifier', Delivery::POST, $item_id);
 	}
 
 	public static function isRemoteSelf($contact, &$datarray)
diff --git a/src/Model/Mail.php b/src/Model/Mail.php
index 9bdb6e1a10..30191edae6 100644
--- a/src/Model/Mail.php
+++ b/src/Model/Mail.php
@@ -13,6 +13,7 @@ use Friendica\Model\Item;
 use Friendica\Database\DBA;
 use Friendica\Network\Probe;
 use Friendica\Util\DateTimeFormat;
+use Friendica\Worker\Delivery;
 
 /**
  * Class to handle private messages
@@ -218,7 +219,7 @@ class Mail
 		}
 
 		if ($post_id) {
-			Worker::add(PRIORITY_HIGH, "Notifier", "mail", $post_id);
+			Worker::add(PRIORITY_HIGH, "Notifier", Delivery::MAIL, $post_id);
 			return intval($post_id);
 		} else {
 			return -3;
diff --git a/src/Model/User.php b/src/Model/User.php
index 64253946fd..b73356306e 100644
--- a/src/Model/User.php
+++ b/src/Model/User.php
@@ -21,6 +21,7 @@ use Friendica\Util\Crypto;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Network;
 use Friendica\Util\Strings;
+use Friendica\Worker\Delivery;
 use LightOpenID;
 
 /**
@@ -912,7 +913,7 @@ class User
 
 		// The user and related data will be deleted in "cron_expire_and_remove_users" (cronjobs.php)
 		DBA::update('user', ['account_removed' => true, 'account_expires_on' => DateTimeFormat::utc('now + 7 day')], ['uid' => $uid]);
-		Worker::add(PRIORITY_HIGH, 'Notifier', 'removeme', $uid);
+		Worker::add(PRIORITY_HIGH, 'Notifier', Delivery::REMOVAL, $uid);
 
 		// Send an update to the directory
 		$self = DBA::selectFirst('contact', ['url'], ['uid' => $uid, 'self' => true]);
diff --git a/src/Module/Admin/Site.php b/src/Module/Admin/Site.php
index 5d2004ca5f..78576efe3b 100644
--- a/src/Module/Admin/Site.php
+++ b/src/Module/Admin/Site.php
@@ -16,6 +16,7 @@ use Friendica\Protocol\PortableContact;
 use Friendica\Util\BasePath;
 use Friendica\Util\BaseURL;
 use Friendica\Util\Strings;
+use Friendica\Worker\Delivery;
 
 require_once __DIR__ . '/../../../boot.php';
 
@@ -99,7 +100,7 @@ class Site extends BaseAdminModule
 			// send relocate
 			$usersStmt = DBA::select('user', ['uid'], ['account_removed' => false, 'account_expired' => false]);
 			while ($user = DBA::fetch($usersStmt)) {
-				Worker::add(PRIORITY_HIGH, 'Notifier', 'relocate', $user['uid']);
+				Worker::add(PRIORITY_HIGH, 'Notifier', Delivery::RELOCATION, $user['uid']);
 			}
 
 			info("Relocation started. Could take a while to complete.");
diff --git a/src/Protocol/Diaspora.php b/src/Protocol/Diaspora.php
index ac1cf9c38d..751033e960 100644
--- a/src/Protocol/Diaspora.php
+++ b/src/Protocol/Diaspora.php
@@ -2148,13 +2148,9 @@ class Diaspora
 			if ($comment['id'] == $comment['parent']) {
 				continue;
 			}
-			if ($comment['verb'] == ACTIVITY_POST) {
-				$cmd = $comment['self'] ? Delivery::COMMENT : 'comment-import';
-			} else {
-				$cmd = $comment['self'] ? Delivery::ACTIVITY : 'activity-import';
-			}
-			Logger::log("Send ".$cmd." for item ".$comment['id']." to contact ".$contact_id, Logger::DEBUG);
-			Worker::add(PRIORITY_HIGH, 'Delivery', $cmd, $comment['id'], $contact_id);
+
+			Logger::info('Deliver participation', ['item' => $comment['id'], 'contact' => $contact_id]);
+			Worker::add(PRIORITY_HIGH, 'Delivery', Delivery::POST, $comment['id'], $contact_id);
 		}
 		DBA::close($comments);
 
diff --git a/src/Worker/APDelivery.php b/src/Worker/APDelivery.php
index 632f6cffc5..fcd4a76725 100644
--- a/src/Worker/APDelivery.php
+++ b/src/Worker/APDelivery.php
@@ -48,7 +48,7 @@ class APDelivery extends BaseObject
 			$data = ActivityPub\Transmitter::createCachedActivityFromItem($target_id);
 			if (!empty($data)) {
 				$success = HTTPSignature::transmit($data, $inbox, $uid);
-				if ($success && in_array($cmd, [Delivery::POST, Delivery::COMMENT])) {
+				if ($success && in_array($cmd, [Delivery::POST])) {
 					ItemDeliveryData::incrementQueueDone($target_id);
 				}
 			}
diff --git a/src/Worker/Delivery.php b/src/Worker/Delivery.php
index 97bc58ef67..ad6bb75c03 100644
--- a/src/Worker/Delivery.php
+++ b/src/Worker/Delivery.php
@@ -27,8 +27,7 @@ class Delivery extends BaseObject
 	const DELETION      = 'drop';
 	const POST          = 'wall-new';
 	const POKE          = 'poke';
-	const COMMENT       = 'comment-new';
-	const ACTIVITY      = 'activity-new';
+	const UPLINK        = 'uplink';
 	const REMOVAL       = 'removeme';
 	const PROFILEUPDATE = 'profileupdate';
 
@@ -319,7 +318,7 @@ class Delivery extends BaseObject
 			// We successfully delivered a message, the contact is alive
 			Model\Contact::unmarkForArchival($contact);
 
-			if (in_array($cmd, [Delivery::POST, Delivery::COMMENT])) {
+			if (in_array($cmd, [Delivery::POST, Delivery::POKE])) {
 				Model\ItemDeliveryData::incrementQueueDone($target_item['id']);
 			}
 		} else {
@@ -400,7 +399,7 @@ class Delivery extends BaseObject
 			// We successfully delivered a message, the contact is alive
 			Model\Contact::unmarkForArchival($contact);
 
-			if (in_array($cmd, [Delivery::POST, Delivery::COMMENT])) {
+			if (in_array($cmd, [Delivery::POST, Delivery::POKE])) {
 				Model\ItemDeliveryData::incrementQueueDone($target_item['id']);
 			}
 		} else {
@@ -411,7 +410,7 @@ class Delivery extends BaseObject
 				Logger::info('Delivery failed: defer message', ['id' => defaults($target_item, 'guid', $target_item['id'])]);
 				// defer message for redelivery
 				Worker::defer();
-			} elseif (in_array($cmd, [Delivery::POST, Delivery::COMMENT])) {
+			} elseif (in_array($cmd, [Delivery::POST, Delivery::POKE])) {
 				Model\ItemDeliveryData::incrementQueueDone($target_item['id']);
 			}
 		}
@@ -439,7 +438,7 @@ class Delivery extends BaseObject
 			return;
 		}
 
-		if (!in_array($cmd, [self::POST, self::COMMENT])) {
+		if (!in_array($cmd, [self::POST, self::POKE])) {
 			return;
 		}
 
diff --git a/src/Worker/Notifier.php b/src/Worker/Notifier.php
index c2f61c55a4..a677cef604 100644
--- a/src/Worker/Notifier.php
+++ b/src/Worker/Notifier.php
@@ -32,23 +32,7 @@ require_once 'include/items.php';
  *
  *		Worker::add(PRIORITY_HIGH, "Notifier", COMMAND, ITEM_ID);
  *
- * where COMMAND is one of the following:
- *
- *		activity				(in diaspora.php, dfrn_confirm.php, profiles.php)
- *		comment-import			(in diaspora.php, items.php)
- *		comment-new				(in item.php)
- *		drop					(in diaspora.php, items.php, photos.php)
- *		edit_post				(in item.php)
- *		event					(in events.php)
- *		like					(in like.php, poke.php)
- *		mail					(in message.php)
- *		suggest					(in fsuggest.php)
- *		tag						(in photos.php, poke.php, tagger.php)
- *		tgroup					(in items.php)
- *		wall-new				(in photos.php, item.php)
- *		removeme				(in Contact.php)
- * 		relocate				(in uimport.php)
- *
+ * where COMMAND is one of the constants that are defined in Worker/Delivery.php
  * and ITEM_ID is the id of the item in the database that needs to be sent to others.
  */
 
@@ -199,7 +183,7 @@ class Notifier
 			}
 
 
-			if (($cmd === 'uplink') && (intval($parent['forum_mode']) == 1) && !$top_level) {
+			if (($cmd === Delivery::UPLINK) && (intval($parent['forum_mode']) == 1) && !$top_level) {
 				$relay_to_owner = true;
 			}
 
@@ -287,8 +271,8 @@ class Notifier
 				// if our parent is a public forum (forum_mode == 1), uplink to the origional author causing
 				// a delivery fork. private groups (forum_mode == 2) do not uplink
 
-				if ((intval($parent['forum_mode']) == 1) && !$top_level && ($cmd !== 'uplink')) {
-					Worker::add($a->queue['priority'], 'Notifier', 'uplink', $target_id);
+				if ((intval($parent['forum_mode']) == 1) && !$top_level && ($cmd !== Delivery::UPLINK)) {
+					Worker::add($a->queue['priority'], 'Notifier', Delivery::UPLINK, $target_id);
 				}
 
 				foreach ($items as $item) {
@@ -545,7 +529,7 @@ class Notifier
 		if (!empty($target_item)) {
 			Logger::log('Calling hooks for ' . $cmd . ' ' . $target_id, Logger::DEBUG);
 
-			if (in_array($cmd, [Delivery::POST, Delivery::COMMENT])) {
+			if (in_array($cmd, [Delivery::POST, Delivery::POKE])) {
 				ItemDeliveryData::update($target_item['id'], ['queue_count' => $delivery_queue_count]);
 			}
 
diff --git a/update.php b/update.php
index 40a3e8ff0d..077a56e66e 100644
--- a/update.php
+++ b/update.php
@@ -362,14 +362,8 @@ function update_1309()
 			continue;
 		}
 
-		if ($item['gravity'] == GRAVITY_PARENT) {
-			$cmd = Delivery::POST;
-		} else {
-			$cmd = Delivery::COMMENT;
-		}
-
 		$deliver_options = ['priority' => PRIORITY_MEDIUM, 'dont_fork' => true];
-		Worker::add($deliver_options, 'Delivery', $cmd, $item['id'], $entry['cid']);
+		Worker::add($deliver_options, 'Delivery', Delivery::POST, $item['id'], $entry['cid']);
 		Logger::info('Added delivery worker', ['command' => $cmd, 'item' => $item['id'], 'contact' => $entry['cid']]);
 		DBA::delete('queue', ['id' => $entry['id']]);
 	}