fixed email settings editing

pub/api/v1/mailsettings/index.php

@@ -20,7 +20,7 @@ if ($API_mailsettings->request_method === 'PUT') {
         'mail_smtp_secure' => ['type' => 'enum', 'values' => ['tls', 'ssl', 'no']],
         'mail_smtp_port' => ['type' => 'int', 'min' => 4, 'max' => 65535],
         'mail_smtp_auth' => ['type' => 'boolean'],
-        'mail_smtp_user' => ['type' => 'email'],
+        'mail_smtp_user' => ['type' => 'string'],
         'mail_smtp_pass' => ['type' => 'string']
     ];
     # check if the password is changed