Mm 46416 add default random message (#21176)

Automatic Merge

app/notification_email.go

@@ -113,7 +113,7 @@ func (a *App) sendNotificationEmail(c request.CTX, notification *PostNotificatio
 		return errors.Wrap(err, "unable to render the email notification template")
 	}
 
-	templateString := "<%s@mattermost.com>"
+	templateString := "<%s@" + utils.GetHostnameFromSiteURL(a.GetSiteURL()) + ">"
 	messageID := ""
 	inReplyTo := ""
 	references := ""