Yes, this has been on here before, but I have never seen a consise answer to the question. Many ISPs block port 25 for our users from home and they use Thunderbird, etc. We are about to migrate over to Zimbra for all 1600 users and I am doing testing before we go to our ownership.
On our existing postfix setup, we have an entry in master.cf:
8025 inet n - n - - smtpd
To allow users to send via port 8025. Since we already have this setup on our existing, and wont have to have users change setup on their machines, does anyone see any problems to this?