IETF
RFC 2821- Simple Mail Transfer Protocol
RFC 2822- Internet Message Format
The MIME Information Page
WHOIS
CompleteWhois (includes hijacks, bogons)
Sendmail
sendmail.org - Sendmail Consortium: a resource for the freeware version of sendmail™
sendmail.net - Sponsored by Sendmail
Procmail
Procmail Homepage
SPF - Sender Policy Framework
Sender Policy Framework
The SPF Record Format and Test Protocol
Authorizing Use of Domains in MAIL FROM (PDF)
SPF - SRS Sender rewriting scheme
SRS - Sender Rewriting Scheme
libsrs_alt :: Home
Sender ID
Sender ID Home Page
DomainKeys
Yahoo! Anti-Spam Resource Center - DomainKeys
DomainKey Library and Implementor's Tools
SpamAssassin
The Apache SpamAssassin Project
Mail::SpamAssassin::Conf - SpamAssassin configuration file
Hashcash
Hashcash.org
DNSBL Homes
Blitzed Open Proxy Monitor
Spam and Open Relay Blocking System (SORBS)
SPAMHAUS
spamcop.net
SURBL
SURBL - Spam URI Realtime Blocklists
Test Sites
SKYLIST | Email Authentication