[Mimedefang] Recipient verification on gateway/secondary-MX

Andrzej Adam Filip anfi at onet.eu
Wed Nov 25 19:58:28 EST 2009

"David F. Skoll" <dfs at roaringpenguin.com> wrote:
> Kevin A. McGrail wrote:
>>> I do something similar - daily LDAP extraction to a database table,
>>> which my filter queries from filter_recipient.  I want to be able to
>>> log failed messages from within my filter, so Sendmail's rejection via
>>> the Access database is too crude for me.  All of my mail servers query
>>> the same database, and also use the database to share
>>> blacklist/greylist/whitelist data, etc.
>> Sure, that will technically will work fine but I think DFS will agree
>> with the statement "Holy Overhead Batman!"
> Ehhmm.. :-)
> Our commercial product offers a huge variety of mechanisms for validating
> recipients:
> 1) You can use LDAP lookups.
> 2) You can do an SMTP callout against a back-end SMTP server.
> 3) You can do a database lookup (PostgreSQL).
> 4) You can supply an arbitrary script that validates the recipient.
> We need the flexibility because of the wide array of mail systems and
> topologies.  On our hosted solution, we cache lookups using memcached
> for efficiency (valid recipients are cached for 24h; invalid ones for
> 1h.)
> Yeah, way more overhead than /etc/mail/access, but in this case it is
> worth it.

Have you ever hit performance problems caused by access table being to
big to be cached in memory?
[sendmail can do 30+ access lookups per one single SMTP session message]

[pl>en: Andrew] Andrzej Adam Filip : anfi at onet.eu
There is only one way to be happy by means of the heart -- to have none.
  -- Paul Bourget

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