i want to setup a mail server behind mikrotik how to forward smtp requests to it?
Are u just using a simple nat setup ??
After you read this http://www.mikrotik.com/Documentation/rosmE.pdf
I cannot find the rule setup in the manual and i cant easily find the manual part of it.
But u should make a dst-nat rule under ip → firewall using winbox that forward tcp port 25 to your mailserver