Re: [Exim] "temporarily unable to verify sender address"

> We have two separate, stable systems running Exim+Mailscanner
> in the separate process mode (-bd incoming, -q1m outgoing,
> with Mailscanner in the middle)
[...]
The upshot of lots of trial & error with this problem is to use
just the queue_only setting and not use the "defer" router/director
technique (as described in the MailScanner Exim doc.),
which seems to conflict with the usual sender_verify/receiver_verify
checks, though not for all senders. I suspect some senders handle
the 451 errors in a way which overcomes the problem.

Ian