[IMail Forum] Prevent spammers from bypassing my MX records

[Andy Paluch]

Using 2 external boxes to filter spam and both MX's point to them. Some spammer is sending emails directly to my IMail box customers and bypassing the MX records when sending mail. I leave port 25 open because my customers (using SMTP AUTH) use the Imail server for outgoing mail.   I notice that version 8.2 of Imail will have an auth only port of 587. That's great to prevent relaying, but will it allow mail NOT to be sent to my local users?   How do I stop this short of having ALL customers change their outgoing mail port to 587 and me blocking port 25 at the Firewall?   Thanks! Andy