[beddo]

Hi there,
I've been using exim smart relays with these for a while:

static_route:
 driver = manualroute
 transport = remote_smtp_smart
 route_data = ${lookup{$domain}lsearch{/etc/staticroutes}}

remote_smtp_smart:
  driver = smtp
  port = 25
  hosts = ${lookup{$domain}lsearch{/etc/staticroutes}}
  hosts_override

This works wonderfully for a lot of our clients and cuts the spam load massively with the spam setup we have. The only limitation that is fairly obvious with this setup is that exim will accept mail for accounts that don't exist on the destination server and it will sit in the queue until it expires.

Then I got to thinking. The Cpanel/exim implementation supports sender verification callouts for incoming mail. Surely there must be some way to adapt a similar feature and have exim do a lookup on the destination server before accepting the mail.

I'm going to have a look and see if I can figure anything out myself but I have no idea where this would even start so if anyone has any pointers or has tried in the past I'd like to know what you came up with or what stopped you.

Cheers.