A SMTP-Proxy that allows authenticated SMTP sessions to traverse, while stopping SMTP sessions from internet worms and SPAM bots.
It can also be used transparently so clients need no additional settings, just use authenticated SMTP connection to their freemail service of choice.
We manage a dormitory campus network (http://www.wh-netz.de) with approx. 3000 students.
BelWü (the scientific network in our state, south-west germany) decided to block TCP port 25 for outgoing connections, to hinder SPAM and internet worms/viruses to be send out from its network to the internet.
They explain their reasons here (in german)To work around this blockade and to enable our users to still use their freemail provider of choise, we decided to create this proxy.
First we searched for a solution on the internet, but we couldn't find one, so we wrote one. We found the (GPLed) perl module MSDW::SMTP (here: http://bent.latency.net/smtpprox/ also some other usage examples) that was written to transparently scan emails for viruses. We are using this module now in our program.
We develope on Debian GNU/Linux i386. The non-transparent version of this proxy should however run everywhere perl runs.
The transparent version is pretty much bound to linux, because it makes use of netfilter logs, to determin the IP address of the destination SMTP server.
Version 0.1 (15kB): authsmtpproxd-0.1.tar.gz ()
Version 0.2 (17kB): authsmtpproxd-0.2.tar.gz ()