chkuser 2.0 -README

Description
===========
The original qmail-smtpd accepts by default all messages, checking later for
the existence of the recipient. So, if the message is delivered to not existing
recipients a lot of additional system work and network traffic are generated,
with multiple expensive bouncing if the sender is a fake one.

chkuser has been developed with the goal to improve the acceptance SMTP phase
of qmail-smtpd. qmail-smtpd patched with chkuser may check the existance of
e-mail recipients immediately in the SMTP acceptance phase of a message and
rejects istantly all messages not directed to existing users, avoiding
additional traffic, work and messages bounced more times.

These goals are achieved enquirying the existing vpopmail archives (each
format is supported: cdb, MySQL, LDAP, etc.) by using standard vpopmail calls,
or using customized chkuser routines.

Version 2.0 - From chkusr to chkuser
====================================
Version 2.0 is a lot different from previous versions, so it deserves a more
evident change in the name.

Version 2.0 has been designed with the goal to be modular, and to make more easy
both adding new features to checkuser code and semplifing code update.

Patching over original qmail files is done over a few points, while the most of
chkuser code remains ouside, in dedicated chkuser's files.

Same for settings, that are inside a dedicated chkuser_settings.h file.

The intention is to semplify upgrading: for future chkuser releases, upgrading
will require only to update chkuser specific files, leaving all the rest
untouched, and changing chkuser_settings.h only if new features must be enabled.

Logging and SPAM
================
chkuser 2.0 has detailed logging of accepted and refused recipients and senders,
allowing a deep analysis of "who's sending to who". This can lead to more
sophisticated future enhancements of anti-SPAM features.

Intrusion rejection
===================
chkuser 2.0 can be tuned to reject sessions exceeding some recipients limits
(limits can be set for max recipients and max not existing recipients). 

URL Location
============
For any new release, support, FAQ, mailing lists, or other information, see:

	http://www.interazioni.it/opensource