We have recently replaced our mail server and initially had an issue as IP mac bind was set against the mac address of the old server. Have changed the bind so that it now matches the MAC of the new server and all was working fine.

About every three days the Draytek will block port 25 to the mail server. If I reboot the router then all returns to normal.

I've no idea why this would suddenly start to block port 25 and would appreciate any help or tips I can use to troubleshoot this and rectify it.

Thanks

do you have any of the CSM P2P files sharing options blocked?
I have found that when all the P2P option are ticked and set t block sometime mail (port 25) is blocked and the syslog categorises it as EDonkey
This is the only time I have ever experienced mail to be blocked