Greylisting deamon: Hermes & libspf2
October 20, 2007 by Yuri Dario
++ From the VOICE OS/2-eCS News Service http://www.os2voice.org ++
From: Yuri Dario
Hermes is an SMTP proxy. We developed hermes for our own use on ITEISA, and we have perfected it with new features to cover our own needs. It is now being made public on the hope that it will help others to stop spam the same way it does for us everyday. What makes it special is that it can be used to stop spam using a combination of the following techniques:
SMTP banner delay
Most spammers will start sending data as soon as the connection is open, without waiting for the SMTP banner. What we do is delay this banner and if we have data waiting before we print it, we drop the connection.
Hermes will process incoming SMTP commands at a slow pace. Most spammers have very little patience, so they will stop sending an email if it's taking too long to deliver.
Greylisting is a process that will delay incoming mails for some minutes before allowing them to be delivered. As most spammers will not resend their messages, you will not receive them. If you want a more technical description, scroll down to read a greylisting description.
As of hermes 1.2 you can now configure hermes to reject emails coming from ips listed on your favourite DNSBL, using the rbl_domain option.
libspf2 implements the Sender Policy Framework, a part of the SPF/SRS protocol pair. libspf2 is a library which allows email systems such as Sendmail, Postfix, Exim, Zmailer and MS Exchange to check SPF records and make sure that the email is authorized by the domain name that it is coming from. This prevents email forgery, commonly used by spammers, scammers and email viruses/worms.
The latest OS/2 build for Hermes (and libspf2) can be found here:
Since this software is ported for free, donations are welcome! you can use PayPal to donate me and support OS/2 developement. If you like to sponsor current OS/2 software developement, follow instructions at