Ubuntu incoming mail server

Question

I am trying to set up and configure a mail server in which I can receive email however I am not having any luck with Postfix or Exim4. I currently have Exim4 configured and it sends mail fine, however it can't receive. When trying to send mail from my other account (gmail) to an account on my server, I get this reply:

Delivery to the following recipient failed permanently:

    root@mydomain.tld

Technical details of permanent failure: 
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 Unrouteable address (state 14).

How can I fix this? Is it an MX record problem or Exim4 configuration error?

Answer 1

Normally you can get your Exim4 on a workable state just using the automatic configuration:

# dpk-reconfigure exim4-config

The most important answers are the ones where you set the type of delivery you want (you want the first one, messages delivered/received directly) and the domain configuration. The domain configuration is a series of questions that asks what domains the server will consider for local delivery and etc. Answering correctly those questions will get your server working.

Answer 2

You can test weather it's a DNS error or exim issue by telnetting directly to the mail server. Then type the SMTP commands manually

telnet youmailserver.net 25
helo server
mail from:test@test.com
rcpt to:test@yourdomin.com
data
test
.

The above is not strictly valid SMTP but should be enough for you to test with.