diff --git a/interface/web/mail/mail_domain_edit.php b/interface/web/mail/mail_domain_edit.php
index 94f2a36fe09e3fed9991e8461bab8184ad0d8951..14ef8e2af9837754a85ac30325fd6b3fe4963ac0 100644
--- a/interface/web/mail/mail_domain_edit.php
+++ b/interface/web/mail/mail_domain_edit.php
@@ -174,6 +174,11 @@ class page_action extends tform_actions {
 			// Clients may not set the client_group_id, so we unset them if user is not a admin
 			if(!$app->auth->has_clients($_SESSION['s']['user']['userid'])) unset($this->dataRecord["client_group_id"]);
 		}
+		
+		//* make sure that the email domain is lowercase
+		if(isset($this->dataRecord["domain"])) $this->dataRecord["domain"] = strtolower($this->dataRecord["domain"]);
+		
+		
 		parent::onSubmit();
 	}
 	
diff --git a/interface/web/mail/mail_user_edit.php b/interface/web/mail/mail_user_edit.php
index 52228a8065bcc77e4293ccd3fd434f81abfba6b4..01e1490a687d35b1e9e9d0ff0083f8373cb9c372 100644
--- a/interface/web/mail/mail_user_edit.php
+++ b/interface/web/mail/mail_user_edit.php
@@ -160,7 +160,7 @@ class page_action extends tform_actions {
 
 		//* compose the email field
 		if(isset($_POST["email_local_part"]) && isset($_POST["email_domain"])) {
-			$this->dataRecord["email"] = $_POST["email_local_part"]."@".$_POST["email_domain"];
+			$this->dataRecord["email"] = strtolower($_POST["email_local_part"]."@".$_POST["email_domain"]);
 		
 			// Set the server id of the mailbox = server ID of mail domain.
 			$this->dataRecord["server_id"] = $domain["server_id"];