Setting up a mail server best practices to be recognized as legitimate

Question

What are the best practices to configure a mail server to have your mail recognized as legitimate non spam messages? Is it to use Domain Keys, Sender ID, Sender Policy Framework, some or all 3 of these together?

Answer 1

There are a few similar mail related questions on SF already, however I'll answer this one as best I can. To avoid being recognised as spam, check:

• You're not on a blacklist
• Your server has MX and reverse DNS records
• You have SPF DNS records (many servers reject mail without a valid SPF, GMail for example, here's an explanation and a wizard)
• Your mailserver's HELO response matches your hostname
• Your mailserver is not an open relay
• Your DNS records' TTL is not too low - 86400 (24 hours) is recommended (some spammers set their TTL very low to regularly update forged DNS records)

I have never required Sender ID, although as it's a Microsoft protocol I'd assume it's more important for Exchange/Live based mail - I have never had problems in this department without implementing Sender ID.

Answer 2

I've found that disabling open SMTP relay, and having valid reverse DNS entries, is a good starting point.

Answer 3

Also don't send spam through it. :)