Spam and open mail relays

Want or need to learn more about how you can prevent unwanted spam (unsolicited bulk e-mail) and open mail relays (which occur when a mail server processes a mail message where neither the sender nor the recipient is a local user)? These resources can help.

Abuse.net:  http://www.abuse.net/relay.html and http://www.abuse.net/tools.html
The Network Abuse Clearinghouse offers an experimental mail relay testing service that runs in anonymous mode and registered user mode. It also offers tools to report spam.

Open Relay Database: http://www.ordb.org/
ORDB.org is a non-profit organization that can assist you in the fight against spam. ORDB.org stores IP addresses of verified open SMTP relays. These relays are, or are likely to be, used as conduits for sending unsolicited bulk e-mail. By accessing this list, system administrators are allowed to choose to accept or deny e-mail exchange with servers at these addresses.

RBLS.org: http://rbls.org/
This site offers an interface and source for checking multiple spam blacklists.

Realtime Blackhole List Lookup: http://www.mob.net/~ted/tools/rbl.php3
A source for checking more than 120 blacklists.

Spam Prevention Early Warning System (SPEWS): http://www.spews.org/index.html
SPEWS is a list of areas on the Internet which system administrators, ISP postmasters, and other service providers have assembled and use to deny e-mail and, in some cases, all network traffic from. This private list is now available for the general public to read and/or use for e-mail filtering.