Things which have changed since I wrote this in 1998
If there is anything else you think should go here, please e-mail
- The MAPS RBL hasn't changed, but I just thought I may as well mention it
again, since it is the main relay blocking list out there.
- ORBS (Open Relay Behaviour-modification System) has moved. The new URL is
http://www.orbs.org/. Any open relays submitted
to the ORBS system will end up on their list.
- RRSS is another RBL-style "relay spam stopper". Their web pages can be
found at http://relays.radparker.com/.
The main differenct from ORBS is that RRSS don't list relays which haven't already
been verified to have been used for spam, whereas ORBS list any which have been
submitted and verified as able to relay spam. RRSS also try not to list
- IMRSS, the Internet Mail Relay Service Survey, at
http://www.imrss.org, provide another list
of open mail relays for potential blocking. This is based on automated
scanning. They have two RBL-like lists, one of open relays and one of
dynamically assigned dial-up IPs (DSSL, dynamic spam sources list), and
provide a patch to the sendmail 8.9.3 distribution to easily enable these.
- MAPS also have a DUL (Dial-Up User List). Blocking e-mail using this
RBL-style database stops you from receiving direct e-mail from
dial-up customers of a number of ISPs who do not filter outgoing SMTP from
their dial-up customers. See
- Yes, you got it, now there's RBL, RRSS, ORBS, IMRSS, DUL and DSSL.
That's a lot of spammer lists. I'm just waiting for the grand unified
DNS server which will answer for machines listed in any of them...
- The software which I mentioned that I use for scanning for mail relays
at UWA is now generally available on my FTP site on Typhaon. Please see
the directory strobe-classb under
and check for the latest version.
- Spammers are getting smarter! They now realise that using a to address
of <"firstname.lastname@example.org"@relay.host.name> will fool a RedHat 5.0, 5.1 or
5.2 host on relay.host.name. This is now checked for by the latest version
of strobe-classb. This problem can be fixed by running a quick little
script I've put together at