diff --git a/mail/postfix/src/opnsense/mvc/app/controllers/OPNsense/Postfix/forms/dialogEditPostfixDomain.xml b/mail/postfix/src/opnsense/mvc/app/controllers/OPNsense/Postfix/forms/dialogEditPostfixDomain.xml
index ce4c6b020..128706a6c 100644
--- a/mail/postfix/src/opnsense/mvc/app/controllers/OPNsense/Postfix/forms/dialogEditPostfixDomain.xml
+++ b/mail/postfix/src/opnsense/mvc/app/controllers/OPNsense/Postfix/forms/dialogEditPostfixDomain.xml
@@ -15,6 +15,6 @@
         <id>domain.destination</id>
         <label>Destination</label>
         <type>text</type>
-        <help>Set the IP or FQDN to where to send the mails to. Empty means MX will be used.</help>
+        <help>Set the IP or FQDN to where to send the mails to. Empty means MX will be used. You can also add custom ports via :225 or disable MX lookup via squared brackets.</help>
     </field>
 </form>
diff --git a/mail/postfix/src/opnsense/mvc/app/models/OPNsense/Postfix/Domain.xml b/mail/postfix/src/opnsense/mvc/app/models/OPNsense/Postfix/Domain.xml
index 168fc7d19..9a14171d0 100644
--- a/mail/postfix/src/opnsense/mvc/app/models/OPNsense/Postfix/Domain.xml
+++ b/mail/postfix/src/opnsense/mvc/app/models/OPNsense/Postfix/Domain.xml
@@ -13,9 +13,11 @@
                                 <default></default>
                                 <Required>Y</Required>
                         </domainname>
-                        <destination type="NetworkField">
+                        <destination type="TextField">
                                 <default></default>
                                 <Required>Y</Required>
+                                <mask>/^([0-9a-zA-Z.:\-\[\]]){1,64}$/u</mask>
+                                <ValidationMessage>Only 64 of the following characters are allowed: 0-9a-zA-Z.:-[]</ValidationMessage>
                         </destination>
             </domain>
         </domains>