My main mail server went down for a few hours today and I have configured a backup mx (also mailcow) at home. Meanwhile backup mx did receive mail while main mx was offline. This was problably not a good idea since my isp is blocking outgoing traffic on port 25. Problem is that backup mx can not push mails to main mx, all i’ll get is connection timed out. Is there a way to force connection other port than 25 from backup mx to main mx?