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Fight spam with unique, blacklistable, expirable email addresses (for Debian Squeeze but adaptable)
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README.md

EXIM4 configuration for Debian Squeeze

Executive Summary

Help fight spams by allowing user control of email validity. Basically:

  • yourname-amazon@your.domain.com -> yourname@your.domain.com if amazon is not blacklisted
  • yourname-2014-01-25@your.domain.com -> yourname@your.domain.com if the expiration date is not reached

The rules

Rewrite localparts to remove chars after a '-', with additional checks:

  • trailing dates in format YYYY-MM-DD are in the past
  • trailing key is not present in not-locals.dbm

Local parts that fails these conditions will be delivered to user fail instead (which is unlikely to exist).

So for instance the email user-2015-12-01@your.domain.com will be delivered (to user@your.domain.com) until the first of January 2012, while user-foobar@your.domain.com will get delivered (to user@your.domain.com) only if user-foobar is not listed in /etc/exim4/no-locals.dbm (Note: it's user-foobar not foobar!).

The two mechanisms can be used together, as long as the expiration date is last.

The purpose of this is to be able to forge unique email addresses that are valid up to a given point.

Makefile

  • make will build not-locals.dbm from not-locals.txt

  • make DOMAIN=your.domain.com install will reload exim with the new configuration

  • make DOMAIN=your.domain.com check will test that the rules are in place and will show some example of what's to expect. Depending on your configuration you may want to replace the user name, though.

Enjoy!

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