Reject large emails

[Joseph Brennan]

--On Tuesday, February 12, 2008 10:58 +0200 Nikos Gatsis <ngatsis at qbit.gr> 
wrote:

> Hello list.
> Is it possible with cyrus to reject emails with large attachments and
> inform the sender for the rejection?


As stated, normally done at the MTA level.  But note also, normally
done by total message size, not attachment size.  If you have to
analyze mime parts and measure the size of each one, half the battle
is lost already, that is the sender already transmitted the large
message and you had to store it in a spool file and parse it.

At MTA level, if you and the sender both use ESMTP, your MTA can state
its maximum message size in the ehlo response, and the sender's MTA can
see that and not even send the message.  That is the best outcome.  If
the sender does not use ESMTP, it wastes time sending the entire
message, but you can still reject quickly.

The sender's MTA will create the bounce notice, or do whatever else
it does when mail can't be delivered.

The Cyrus system should not send a bounce.  It should only accept or
reject, and the sending MTA should handle notifying the sender.

Joseph Brennan
Columbia University Information Technology