Question : Kerio Mail Server 6.7.2 SMTP Port 25

I have setup a KMS 6.7.2 running Secure STMP, Secure IMAP, Secure LDAP, Secure HTTP. I am the MX for the domain. I have SMTP service on port 25 open, but only allowing relay from authenticated users.

When I block it and run the Mail Server Test Center tools from DNSStuff it gives an error, and no email is delivered to the server.

I just need a straight answer. Do I need to have port 25 open to accept email? Am I missing a simple premise of email?

Answer : Kerio Mail Server 6.7.2 SMTP Port 25

I can't think of any reason for you to close port 25 on your firewall if you're running an SMTP server.  What you do need to do though is configure your firewall so that port 25 is only open on the external IP address that is associated with your e-mail server and you have the necessary translation rule through to the internal IP of your Kerio server.  Also, make sure that outbound SMTP is only allowed from your e-mail server.

As long as you don't have the 'Open Relay' option selected  on the 'Relay Control' tab, then you will be ok.