diff --git a/src/applications/auth/storage/PhabricatorAuthMessage.php b/src/applications/auth/storage/PhabricatorAuthMessage.php
--- a/src/applications/auth/storage/PhabricatorAuthMessage.php
+++ b/src/applications/auth/storage/PhabricatorAuthMessage.php
@@ -61,14 +61,20 @@
     return $this->getMessageType()->getDisplayName();
   }
 
-  public static function loadMessageText(
+  public static function loadMessage(
     PhabricatorUser $viewer,
     $message_key) {
-
-    $message = id(new PhabricatorAuthMessageQuery())
+    return id(new PhabricatorAuthMessageQuery())
       ->setViewer($viewer)
       ->withMessageKeys(array($message_key))
       ->executeOne();
+  }
+
+  public static function loadMessageText(
+    PhabricatorUser $viewer,
+    $message_key) {
+
+    $message = self::loadMessage($viewer, $message_key);
 
     if (!$message) {
       return null;
diff --git a/src/applications/people/controller/PhabricatorPeopleWelcomeController.php b/src/applications/people/controller/PhabricatorPeopleWelcomeController.php
--- a/src/applications/people/controller/PhabricatorPeopleWelcomeController.php
+++ b/src/applications/people/controller/PhabricatorPeopleWelcomeController.php
@@ -48,26 +48,38 @@
       return id(new AphrontRedirectResponse())->setURI($profile_uri);
     }
 
+    $default_message = PhabricatorAuthMessage::loadMessage(
+      $admin,
+      PhabricatorAuthWelcomeMailMessageType::MESSAGEKEY);
+    if (strlen($default_message->getMessageText())) {
+      $message_instructions = pht(
+        'The email will identify you as the sender. You may optionally '.
+        'replace the [[ %s | default custom mail body ]] with different text '.
+        'by providing a message below.',
+        $default_message->getURI());
+    } else {
+      $message_instructions = pht(
+        'The email will identify you as the sender. You may optionally '.
+        'include additional text in the mail body by specifying it below.');
+    }
+
     $form = id(new AphrontFormView())
       ->setViewer($admin)
-      ->appendInstructions(
+      ->appendRemarkupInstructions(
         pht(
           'This workflow will send this user ("%s") a copy of the "Welcome to '.
           'Phabricator" email that users normally receive when their '.
           'accounts are created by an administrator.',
           $user->getUsername()))
-      ->appendInstructions(
+      ->appendRemarkupInstructions(
         pht(
           'The email will contain a link that the user may use to log in '.
           'to their account. This link bypasses authentication requirements '.
           'and allows them to log in without credentials. Sending a copy of '.
           'this email can be useful if the original was lost or never sent.'))
-      ->appendInstructions(
-        pht(
-          'The email will identify you as the sender. You may optionally '.
-          'include additional text in the mail body by specifying it below.'))
+      ->appendRemarkupInstructions($message_instructions)
       ->appendControl(
-        id(new AphrontFormTextAreaControl())
+        id(new PhabricatorRemarkupControl())
           ->setName('message')
           ->setLabel(pht('Custom Message'))
           ->setValue($v_message));
diff --git a/src/applications/people/mail/PhabricatorPeopleMailEngine.php b/src/applications/people/mail/PhabricatorPeopleMailEngine.php
--- a/src/applications/people/mail/PhabricatorPeopleMailEngine.php
+++ b/src/applications/people/mail/PhabricatorPeopleMailEngine.php
@@ -58,4 +58,15 @@
     throw new PhabricatorPeopleMailEngineException($title, $body);
   }
 
+  final protected function newRemarkupText($text) {
+    $recipient = $this->getRecipient();
+
+    $engine = PhabricatorMarkupEngine::newMarkupEngine(array())
+      ->setConfig('viewer', $recipient)
+      ->setConfig('uri.base', PhabricatorEnv::getProductionURI('/'))
+      ->setMode(PhutilRemarkupEngine::MODE_TEXT);
+
+    return $engine->markupText($text);
+  }
+
 }
diff --git a/src/applications/people/mail/PhabricatorPeopleWelcomeMailEngine.php b/src/applications/people/mail/PhabricatorPeopleWelcomeMailEngine.php
--- a/src/applications/people/mail/PhabricatorPeopleWelcomeMailEngine.php
+++ b/src/applications/people/mail/PhabricatorPeopleWelcomeMailEngine.php
@@ -49,9 +49,6 @@
     $sender = $this->getSender();
     $recipient = $this->getRecipient();
 
-    $recipient_username = $recipient->getUserName();
-    $is_serious = PhabricatorEnv::getEnvConfig('phabricator.serious-business');
-
     $base_uri = PhabricatorEnv::getProductionURI('/');
 
     $engine = new PhabricatorAuthSessionEngine();
@@ -99,13 +96,9 @@
       $message[] = pht('  %s', $base_uri);
     }
 
-    $custom_body = $this->getWelcomeMessage();
-    if (strlen($custom_body)) {
-      $message[] = $custom_body;
-    } else {
-      if (!$is_serious) {
-        $message[] = pht("Love,\nPhabricator");
-      }
+    $message_body = $this->newBody();
+    if ($message_body !== null) {
+      $message[] = $message_body;
     }
 
     $message = implode("\n\n", $message);
@@ -116,4 +109,27 @@
       ->setBody($message);
   }
 
+  private function newBody() {
+    $recipient = $this->getRecipient();
+
+    $custom_body = $this->getWelcomeMessage();
+    if (strlen($custom_body)) {
+      return $this->newRemarkupText($custom_body);
+    }
+
+    $default_body = PhabricatorAuthMessage::loadMessageText(
+      $recipient,
+      PhabricatorAuthWelcomeMailMessageType::MESSAGEKEY);
+    if (strlen($default_body)) {
+      return $this->newRemarkupText($default_body);
+    }
+
+    $is_serious = PhabricatorEnv::getEnvConfig('phabricator.serious-business');
+    if (!$is_serious) {
+      return pht("Love,\nPhabricator");
+    }
+
+    return null;
+  }
+
 }