Re: [Exim] MAIL ACL and sender verification

Alan J. Flavell wrote:

> From even my limited experience, there seem to be nontrivial numbers
> of mailers which react to 5xx responses at various stages either by
> proceeding as if nothing had gone wrong, or by treating the 5xx as a
> temporary failure (e.g many of the hosts that we reject because they
> presented illegal character(s) in the HELO string).
>
> So far, it seems that the best chance for getting rid of bad mail
> detected in earlier phases is to postpone the 5xx response until the
> RCPT TO phase.
>
>
Agreed, I am checking some things at MAIL FROM: time, but only so I can insert
delays into the connection to slow them down a bit...