On Fri, 2007-11-02 at 04:24 -0700, ikearns wrote:
> However any mail that does get through that is destined for a resolvable
> email address will then be delivered to the back end server(s) via and Exim
> box running manualroutes. Should this message be undeliverable (through the
> mailbox not existing) then this is sent back to the sender. I believe this
> is common practise and as describes, required as a NDR.
OK, so you could therefore do:
require verify = recipient/callout
domains = +local_domains
or a variant thereof, in an appropriate place in your ACLs - perhaps in
the RCPT ACL, so it's done *before* spam and virus scans take place.
This way Exim will call forward to the backend servers and validate the
recipient address as part of the SMTP transaction, thus saving on AS/AV
resources since the RCPT call will be rejected before DATA if the
recipient mailbox is invalid.
Your backend servers will then not generate any NDRs since invalid
recipients will never get to them.
This depends, of course, on your backend servers being able to reject at
RCPT time rather than doing accept-and-bounce.
Graeme
