We frequently would LOVE to be able to communicate with them to ask why
they are rejecting messages legitimate randomly, or whatever. Or, we'd
like to tell them that one of their customers has set up forwarding from
a proper email address to one of theirs, so THAT is why they're
receiving so much spam from this IP address. And so on.
No doubt all of your mail is fine and virtuous (although if you let
your users forward without filtering, it's a self-inflicted wound),
but I can assure you that the vast majority of people who would want
to make such calls are dodgy ESPs and spammers, to whom the answer is
we're not accepting your mail because our users don't want it, and no,
we don't care about your business model.
Talk about something that doesn't scale.
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