Mailing List Message #92232
From: Jon R. Doyle <>
Date: Wed, 15 Aug 2007 12:05:55 -0700
To: <>
X-Mailer: CommuniGate Pro Pronto 1.2s

Hello all,
We are getting ready to move our clients from sending smtp on port 25 to sending on a different port to >avoid problems with ISPs blocking outbound port 25 traffic. However, we have a group of test users >who are using MAPI, and we have not been able to find the setting to change the outbound port. Could >anyone offer some clarification? Does a MAPI connection do everything through port 143?

yes, the MAPI connector uses extended MAPI capabilities to do everything over that port. It is always a good idea to use SSL or port 993 for the MAPI connector, as all your remote users will then have secure connections. Most WiFI and DSL networks I have experienced do not block 993.

Port 25 is/was generally meant for MTA to MTA traffic, and we are seeing all major ISP/broadband operators moving to restrict usage of port 25 by clients inside their network, or more over trying to connect to remote port 25 "systems"

Clients (not our MAPI) should use port 587 with Authentication, most ISPs permit this too that I am aware of.


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