- experiment with throttling

- make config parser aware of supported options and complain about unsupported ones

- modularize the whole process

- make SQLgrey manageable by Postfix's master daemon

- dsn_awl (for MAIL FROM: <>), connect_awl (first stage before from_awl), rcpt_awl (match forwards)

- make header content user configurable with some predefined macros.
  _DELAY_ for example.

- add automatic blacklisting support (ideas: spamtraps, no reconnect and more than x rejects, ...).

- use time units everywhere to make configuration easier

- experiment with an adaptive cleanup algorithm

- create a stress-testing suite (for performance/reliability tests)

- check if permission related SQL errors are catchable

- try to exit with a proper error code when database is unavailable or the user
  doesn't have enough rights to access the pid-file

- add sender e-mail based white-list with huge warnings

- experiment with SPF support

- support migrating from another grey-lister by calling it to learn its auto-white-lists