I have an ispconfig installation done following the official tutorial on Ubuntu 18.04 with postfix and dovecot mail server, the mail server seems to function ok and sending receiving emails works but I have an issue I need to work around. Emails from certain government institutions are not received, they seem to have problems with their email server, their reverse dns lookup is not working which is suspect is the reason why the emails are not even received. Can anyone provide any tips how can I work around this, I've checked logs but nothing out of the ordinary or I am looking in the wrong places, is this something that can be adjusted on postfix or? Thanks.
If you need to receive emails from servers that have no valid reverse dns, then you'll have to disable the reverse checks in postfix main.cf file.
