Re: [exim] Brain Teaser - how would you do this?

Tony Finch wrote:

> On Tue, 4 Apr 2006, W B Hacker wrote:
>
>>>require verify = recipient/callout
>>
>>Well - yes, if on the same server ....
>
>
> No, callouts work across servers. We use this on the MXs in Cambridge to
> verify addresses in departments such as the Computer Lab that run their
> own email servers. It also works for organizations such as the University
> Press for which we act as a secondary MX.
>
> Tony.

Surely they are *intended* to do so, and certainly may do if all
is well. Better than 'ident' for sure...

But I am sure you know at least as well as I how unpredictable
they can be in the smtp world-at-large - especially given the
mix of brazillions of minor players with who-knows-how config
and certain 'major' ISP's who would just as soon blacklist those
who query their servers regularly, then abort w/o traffic - even
on sender verification.

I'd have to be convinced that off-box pre-delivery recipient
callouts earned their overhead vs simple 'send-it-and-see'.

On-box or within-known-network / affinity group, where you can
talk to the folks running 'em is a whole 'nuther critter.

In Marc's case, I remain baffled as to where checking for an
address that was of his own 'generated ..' and '.. arbitrary'
devising is needed / useful instead of a more direct method.

Bill