How Do I Configure My Mail Server to Use Alternate-Port SMTP with Authentication?

Here are some links to documentation on setting up mail servers to use an SMTP gateway for all outgoing mail with authentication. This is only a short list of popular MTAs. For other mail servers please consult their documentation or contact the publishers technical support.

Exchange A Quick Guide to Using Alternate-port SMTP with Exchange
Exim Exim 4.10 Specification, 32.5. Authentication by an Exim client
MDaemon User Manual pages 48-49, Section Setup Menu under Server Settings in the Port section you can change the port your Smart Host is set to use. Then go to the User Manual pages 111-114, Section Domain Manager then Smart Host.
Home > Downloads > MDaemon Messaging Server > ManualNOTE: MDaemon 7.0 & 7.1 have a bug which causes the AUTH request to not be sent when using an alternate port. Please use a previous version or get an update from Alt-N (not available as of 2004-06-24)
Postfix Postfix official documentation is the first place to start or you can use No-IP’s Postfix guide.
Qmail Remote-Auth Patch
Sendmail Configuring Sendmail for use with Alternate-port SMTP
Sendmail Official documentation – SMTP-AUTH Client with Sendmail