diff --git a/boot.php b/boot.php
index eafbc8da9..4c16f59d6 100644
--- a/boot.php
+++ b/boot.php
@@ -140,7 +140,6 @@ define('MAX_LIKERS',    75);
  * Email notification options
  * @{
  */
-define('NOTIFY_MAIL',        16);
 define('NOTIFY_SUGGEST',     32);
 define('NOTIFY_PROFILE',     64);
 define('NOTIFY_TAGSELF',    128);
diff --git a/include/enotify.php b/include/enotify.php
index 4c4e7e10d..ad141e1c4 100644
--- a/include/enotify.php
+++ b/include/enotify.php
@@ -102,7 +102,7 @@ function notification($params)
 	$hsitelink = '';
 	$itemlink  = '';
 
-	if ($params['type'] == NOTIFY_MAIL) {
+	if ($params['type'] == Notify\Type::MAIL) {
 		$itemlink = $siteurl.'/message/'.$params['item']['id'];
 		$params["link"] = $itemlink;
 
diff --git a/mod/message.php b/mod/message.php
index d1d3e89df..bba530ca5 100644
--- a/mod/message.php
+++ b/mod/message.php
@@ -13,6 +13,7 @@ use Friendica\Database\DBA;
 use Friendica\DI;
 use Friendica\Model\Contact;
 use Friendica\Model\Mail;
+use Friendica\Model\Notify\Type;
 use Friendica\Module\Security\Login;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Proxy as ProxyUtils;
@@ -338,10 +339,10 @@ function message_content(App $a)
 
 			if ($message['convid']) {
 				// Clear Diaspora private message notifications
-				DBA::update('notify', ['seen' => 1], ['type' => NOTIFY_MAIL, 'parent' => $message['convid'], 'uid' => local_user()]);
+				DBA::update('notify', ['seen' => 1], ['type' => Type::MAIL, 'parent' => $message['convid'], 'uid' => local_user()]);
 			}
 			// Clear DFRN private message notifications
-			DBA::update('notify', ['seen' => 1], ['type' => NOTIFY_MAIL, 'parent' => $message['parent-uri'], 'uid' => local_user()]);
+			DBA::update('notify', ['seen' => 1], ['type' => Type::MAIL, 'parent' => $message['parent-uri'], 'uid' => local_user()]);
 		} else {
 			$messages = false;
 		}
diff --git a/mod/ping.php b/mod/ping.php
index 580d82a95..f91a1753c 100644
--- a/mod/ping.php
+++ b/mod/ping.php
@@ -405,7 +405,7 @@ function ping_get_notifications($uid)
 			AND $seensql `notify`.`seen` ORDER BY `notify`.`date` $order LIMIT %d, 50",
 			intval($uid),
 			intval(Type::INTRO),
-			intval(NOTIFY_MAIL),
+			intval(Type::MAIL),
 			intval($offset)
 		);
 
diff --git a/mod/settings.php b/mod/settings.php
index 363501852..7ae0f6479 100644
--- a/mod/settings.php
+++ b/mod/settings.php
@@ -1234,7 +1234,7 @@ function settings_content(App $a)
 		'$notify2'	=> ['notify2', DI::l10n()->t('Your introductions are confirmed'), ($notify & Type::CONFIRM), Type::CONFIRM, ''],
 		'$notify3'	=> ['notify3', DI::l10n()->t('Someone writes on your profile wall'), ($notify & Type::WALL), Type::WALL, ''],
 		'$notify4'	=> ['notify4', DI::l10n()->t('Someone writes a followup comment'), ($notify & Type::COMMENT), Type::COMMENT, ''],
-		'$notify5'	=> ['notify5', DI::l10n()->t('You receive a private message'), ($notify & NOTIFY_MAIL), NOTIFY_MAIL, ''],
+		'$notify5'	=> ['notify5', DI::l10n()->t('You receive a private message'), ($notify & Type::MAIL), Type::MAIL, ''],
 		'$notify6'  => ['notify6', DI::l10n()->t('You receive a friend suggestion'), ($notify & NOTIFY_SUGGEST), NOTIFY_SUGGEST, ''],
 		'$notify7'  => ['notify7', DI::l10n()->t('You are tagged in a post'), ($notify & NOTIFY_TAGSELF), NOTIFY_TAGSELF, ''],
 		'$notify8'  => ['notify8', DI::l10n()->t('You are poked/prodded/etc. in a post'), ($notify & NOTIFY_POKE), NOTIFY_POKE, ''],
diff --git a/src/Model/Mail.php b/src/Model/Mail.php
index de351db4a..9735a795a 100644
--- a/src/Model/Mail.php
+++ b/src/Model/Mail.php
@@ -10,6 +10,7 @@ use Friendica\Core\System;
 use Friendica\Core\Worker;
 use Friendica\DI;
 use Friendica\Database\DBA;
+use Friendica\Model\Notify\Type;
 use Friendica\Network\Probe;
 use Friendica\Protocol\Activity;
 use Friendica\Util\DateTimeFormat;
@@ -68,7 +69,7 @@ class Mail
 
 		// send notifications.
 		$notif_params = [
-			'type' => NOTIFY_MAIL,
+			'type' => Type::MAIL,
 			'notify_flags' => $user['notify-flags'],
 			'language' => $user['language'],
 			'to_name' => $user['username'],
diff --git a/src/Model/Notify/Type.php b/src/Model/Notify/Type.php
index 440dde63e..fbc31da37 100644
--- a/src/Model/Notify/Type.php
+++ b/src/Model/Notify/Type.php
@@ -15,4 +15,6 @@ class Type
 	const WALL = 4;
 	/** @var int Notification about a followup comment */
 	const COMMENT = 8;
+	/** @var int Notification about a private message */
+	const MAIL = 16;
 }
diff --git a/src/Module/Delegation.php b/src/Module/Delegation.php
index eb38f0289..b5e4c1a90 100644
--- a/src/Module/Delegation.php
+++ b/src/Module/Delegation.php
@@ -112,7 +112,7 @@ class Delegation extends BaseModule
 
 			$identities[$key]['selected'] = ($identity['nickname'] === DI::app()->user['nickname']);
 
-			$condition = ["`uid` = ? AND `msg` != '' AND NOT (`type` IN (?, ?)) AND NOT `seen`", $identity['uid'], Type::INTRO, NOTIFY_MAIL];
+			$condition = ["`uid` = ? AND `msg` != '' AND NOT (`type` IN (?, ?)) AND NOT `seen`", $identity['uid'], Type::INTRO, Type::MAIL];
 			$params = ['distinct' => true, 'expression' => 'parent'];
 			$notifications = DBA::count('notify', $condition, $params);