Giuliano> could you expand on that please? I also think exim sender
Giuliano> callout has its shorcomings and that, although sender
Giuliano> callout can never be perfect, it could be improved. We
Giuliano> might have different ideas on where it should be improved.
There's one known case (though it has not actually happened yet to my
knowledge) where enabling sender callout will cause a site to fail to
receive mail from us; if you make the callout attempts from an IP
address which is listed on a dynamic-IPs list (currently
dynablock.easynet.nl), or on one of a number of proxy and spam-sources
blacklists, then the default timeouts will be too short to get the
successful response from the verification, and you'll just defer the
message forever unless you lengthen the timeout (to at least a couple
of minutes) or set defer_ok.
