From the MDaemon console: 

Click Setup

Click Server Settings 

Click Domain Sharing

Check Enable Domain Sharing

In the Host or IP field, enter the host name or IP address of an MDaemon server which you are using Domain Sharing

If you are using a non-standard Minger port (4069) change the entry in the Minger port field. (Most likely, you'll keep this at 4069.)

If you are requiring a password for Minger queries on the shared server, enter it in the Minger password field

Click Add  

Repeat steps 6-9 for any other MDaemon servers with which you are using Domain Sharing

Note that this requires the Minger service on all the MDaemon servers in use to be activated. To activate Minger, follow these steps: 

Click on the Accounts menu

Choose Account Options  

Click Minger

Check Enable Minger server

If you wish to use a non-standard port for Minger queries, change the entry in Listen for Minger connections on this UDP port field

If you wish to require a password for queries, select Minger queries require a shared secret field

Click OK

Notes

MDaemon will also query any servers listed under the Domain Sharing settings for local accounts and incoming messages sent from local accounts if they are not listed in the current server's database.

This article refers to MDaemon 10.x and above.

Note: You can append a colon and port (i.e mail.example.com:2525), if you wish to use a specific, non-default port when sending SMTP messages to the host (this is not the same as the Minger port). The option to set this up is under, Setup > Default Domain & Servers > Domain Sharing tab > Host or IPsection.