Ok, I can add it in admin web UI. I tried add domain ‘sub.domain.domian’ which same as MAILCOW_HOSTNAME. But it shows “Domain cannot match hostname”. That is a really confusing message that makes me think you can not use subdomain as email address postfix. Later I find it should be NOT same as host name and i tried to add ‘sub1.domain.domian’ then it works.
But how to deal with ‘autodiscover’ and ‘autoconfig’?