I recently setup an exim4 server instance only for the purpose of allowing our host to send outgoing emails (the application hosted therein sends a number of automated email messages).
Recently the box lost the ability to send mail -- upon examining the response from the destination SMTP hosts, we were apparently flagged and "blacklisted" as a host for spam. I looked at the logs and we haven't been relaying anything -- only sending messages as the host for which I've configured the server.
Anyway, I am in no way an expert on email -- frankly I think email is a solution that has been horribly overcomplicated due to POS spammers. Never the less, I'd really appreciate some help in figuring out how to configure things properly such that we don't get black listed again (I've submitted a request to remove the host from the blacklist). Accordingly, here's a quick walk-through of the steps I've taken to try to fix the issue:
For purpose of example, lets say the host is hosting the site:
And we're sending email as
1) dpkg-reconfigure exim4-config
2) Standard configuration (SMPT to send and receive, no smarthost), domain name set at sampledomain.com. Listening only on 127.0.0.1.
3) Reverse DNS for www.sampledomain.com points to the host's static IP address.
4) SPF record added for the host to accept mail for sampledomain.com
Thats it. This is all I've typically had to do with a mail server to get things working -- rDNS and SPF being the critical factors.
Anyway, I appreciate any feedback -- I'm sure there may be something I'm missing.