Re: [Exim] Sender Verify

Hi Ron, on Thu, 01 Jul 2004 14:44:08 +0100 you wrote:

> Looking at page 339/50 of Phils's book, I am still not clear on how far
> sender verify goes. It implies that it is only interested in where it
> can send a bounce message to, so does that mean if it can find an mx
> value for the domain part then it is happy ?

It depends whether you use the "callout" option or not. Without the
callout option (which is the default configuration), it just runs the
address through the routers and makes sure that it can route the address,
which will (typically) include checking that DNS is working and has some
reasonable destination hosts that aren't in ignore_target_hosts.

If you use the "callout" option, Exim will go as far as making a
connection to the alleged sender's domain mail system and running through
an SMTP session up to the RCPT TO stage (using the null sender), to see if
that works. There is obviously a resource usage penalty for both you and
the supposed sender if you do callouts, and some people object to them.
(And of course, it won't help for those unfortunate people who accept
mails at SMTP time and then generate bounce messages for those that can't
be delivered).

Tim