Topic: Mail server problem - Maybe NAT?

[dough]

I have setup a SME server 7.3 (latest) in server-only mode.
Everything works fine from outside and inside the network on WEB and incoming IMAP mail connection.
The SMTP server works fine on the internal network.

BUT, when I send an e-mail to an address on the server, I get an error after about 24hours: Connection timed out.

I'm able to ping the mail.domain.com and the DNS has been set as follow:

A-Records:
*.domain.com -> My external IP (Static)
domain.com -> My external IP (Static)

MX record:
Host: domain.com -> Mail exchanger: mail.domain.com
mail.domain.com -> domain.com

I have forwarded ports from my D-Link router to the local server IP on these ports:
21, 25, 2525, 465, 993, 1721, 80, 143

I have a similar server another place, where this works fine.

Could it be a NAT problem or maybe some kind of blocking from the ISP?

[CharlieBrady]

Could it be a NAT problem or maybe some kind of blocking from the ISP?

The latter is common.

[mmccarn]

You can use a tool like Shields Up! to scan the WAN IP of your network and tell you what ports are open.

If port 25 remains closed no matter what you do, it's probably being blocked by  your ISP.