Making SpamAssassin work
Making DMARC and SPF work
Making DKIM work
Making Majordomo work (I used to recommend this)
Making Mailman work (I now recommend this)
email server -- pop3 and imap
Using Blocklists (general)
MAPS RBL-PLUS (using the MAPS blocklist -- specific)
Milter (using Milter with sendmail)
Mail/AUTH/sasl (using AUTH with sendmail)
STARTTLS
restarting sendmail (after every config change)
basic sendmail configuration tips
Useful sendmail-related websites:
Brandon Hutchinson.com on "sendmail panic: cannot save rejected email anywhere
Useful spam-related websites:
Vintners.net spam management page.
Mail Abuse Prevention System (MAPS) (a paid subscription service)
`telnet mail-abuse.com` (tests your email config for relay)
Abuse.Net abuse reporting system
Sendmail & virtusertable (scomm.org),
(local copy)
sendmail.org
cauce.com