Q:

hMailServer and reverse DNS

I have an hMailServer installation on a Windows 2012 server VM and need to properly set up reverse DNS + the mail server in order to avoid getting e-mails bounced back from certain big providers, which started to check this recently.
My server provider allows to set one rDNS entry, however I'm hosting several domains. So, I wonder what to set there and how to configure hMailServer.
There is a Default domain setting in the Advanced settings, but the help says this is only used for user which log in without an explicit domain. So, how can I configure hMailServer to use always the domain I set for rDNS?

A:

Your answer is here: https://www.hmailserver.com/documentation/latest/?page=reference_protocolsmtp
Under SMTP Settings >> Hostname. Change the Hostname setting to be whatever the public IP address's rDNS is.

It does not matter what host name you enter, as long as it resolves to
  the IP address where hMailServer is running. You may have 15 different
  host names which resolves to the IP address hMailServer is running on.
  If this is the case, you can enter any of these 15 different host
  names in the Host name field.

