I'll expand a little on John's comments below
On 29/11/12 18:44, John Hardin wrote:
On Thu, 29 Nov 2012, Ed Flecko wrote:
I'll be sure to check into Postgrey.
Are there any special considerations to installing/configuring it or
is it simply a matter of installing, reading the docs and configuring?
The biggest consideration is not technical, it's managing the
expectations of your users.
You will need to educate your users that email is *not* instant messaging.
Indeed. But do also play around with the delays in postgrey (--delay). A
minimal delay of 60 seconds is enough to force a retry and is adequate -
legit hosts will retry, non-legit hosts won't so a longer delay is
generally unnecessary.
You will probably want to put a little effort into maintaining lists of
regular correspondents who can bypass greylisting. There may be tools to
automate that, e.g. to whitelist someone a local user has sent mail to.
Postgrey has an auto-whitelisting mechanism that can be fine tuned by
reducing the number of times a client must successfully retry
(--auto-whitelist-clients) before auto-whitelisting and adjusting the
age of the cache (--max-age) so whitelisted clients are cached for longer.
Generally after a couple weeks of normal mail flow, all regular hosts
should be cached so only new contacts will get greylisted. Also don't be
afraid to whitelist big clients that you receive correspondence from -
you know they are legit and will resend so it's pointless greylisting them.
Postgrey is very configurable and all the options above are documented
in the manpage.
Some users are extremely allergic to any delays in their email; you may
have to maintain a list of exception destination addresses to keep them
happy, or for addresses where no delay is acceptable, e.g. <support@...>
or <sales@...>
