I have three servers runing Virtualmin with multiple domains each. Email works great for all servers. However, only issue I have is with one server when someone sets up Gmail to retrieve /send mail. They can receive email fine but when you go to setup Gmail to send using their mail server it will never connect (I tried port 25, 587 and 465). Outlook and even other webmail clients work fine it's just Gmail, and only on this one server. I have tested this for multiple domains on the server as well and same issue. Below are some maillog entries...
lost connection after UNKNOWN from mail-pd0-f170.google.com[18.104.22.168]
Jan 12 21:38:16 web04 postfix/smtpd: disconnect from mail-pd0-f170.google.com[22.214.171.124]
Been working on this for days and can't find a solution. Thanks