Hi. I'm running on ec2 (if relevant) and ran through the perfect-server-debian-lenny-ispconfig3 tut.
The registrar is Godaddy, and I've set up hosts ns1 and ns2 to point to my servers IP, and set the nameserver entries to the above. I used to run my own Plesk box on a DSL with the same config, and all worked as expected, so I don't think the problem is here.
I added a DNS zone in ispconfig:
A domain.com 123.456.789.123 0
CNAME www.domain.com domain.com 0
MX domain.com mail.domain.com 10
NS domain.com ns1.domain.com 0
NS domain.com ns2.domain.com 0
An Email Domain:
And mailbox with receiving enabled.
I can send email to external addresses from this account via squirrelmail, and through external email programs such as Mail (though, both the incoming and outgoing servers will only work if entered like "domain.com" as opposed to "mail.domain.com" in the external email client config - don't know why). These emails are received by the external accounts fine. But when I reply, nothing happens. No bounce, no errors in the logs, nothing in the queue. Just silent failure. However, if I send the email to its own address (e.g. from: firstname.lastname@example.org to:email@example.com) it works, even from external email client.
I was having problems with clamav after install. Out of date errors, and unable to update errors. I disabled clamav by commenting out the call to it in /etc/amavis/conf.d/15-av_scanners while I try to get everything working.
When I ran through ISPConfig, I used the given public dns name as the fqdn (something like ec2-00-00-00-00.compute-0.amazonaws.com).
tl;dr: email can go out, but can't come in.
Thanks for any tips/direction!