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How to fight SPAM
By Uwe Holz
More information about SPAM and anti SPAM efforts can be found at http://spam.abuse.net.
Last Update: Monday, July 07, 2003
SPAM is the usual expression for unsolicited e-mails. The term stands for Spiced Ham or SPread Around Message. Other sources are stating that the origin of the word SPAM comes from this Monthy Python sketch.
Anyway, SPAM is annoying and a real pain, because it costs billions of dollars, mostly paid by Internet Service Providers (ISP).
Legal resources against SPAM senders are not sufficient enough and SPAM developers are hiding themselves by different tricks. One of the most popular is using a foreign mail server for sending out all the junk, which assumes the existence of badly configured SMTP servers, so called Open Relays.
Properly set up servers only accept e-mails sent to members of the specified intranet domain (inbound direction) and require authentication for mail relaying (outbound direction). Authentication techniques are SMTP AUTH or POP before SMTP.
The following test can be used to determine, whether the specified mail server is "tight" against open relay attempts or not. To do so just type in the dotted mail server name and hit the go button.
The test above is using a CGI application called chkrelay, which works based on its configuration file chkrelay.ini. Every test is defined by one section containing a couple of SMTP client commands like follows:
[MAIL1]
HELO=HELO www.kickspamtoa.com
FROM=support@-MAILDOAMIN
TO=postmaster%test.net@-MAILSERVERIP
[MAIL2]
HELO=HELO www.chk.com
FROM=chkrelay
TO=postmaster@kickspamtoa.com
...The test is fully configurable and can be used as CGI script or command line tool. Archive file chkrelay-10.zip contains binaries for Windows and Linux, cross platform C++ source code and make files for WIN32 and Linux.