If you’ve been using SpamAssassin and have been reporting to SpamCop then you’ll have found overnight that you got a heap of bounces back saying things like:
<email@example.com> (expanded from <firstname.lastname@example.org>): unknown user: "devnull"
It turns out that the email@example.com appears to be something that the SpamAssassin developers set without consulting with SpamCop, and SpamCop have just been blackholing those reports for an unknown amount of time. Last night it went away and so now IronPort are rejecting them which was how I learnt of this. I’m not impressed by what the SA developers did her, it should have required you to put in a registered SpamCop address and not reported if that wasn’t set.
I’ve disabled my SpamCop reporting by commenting out this line in
/etc/mail/spamassassin/v310.pre on my Debian mailserver:
If you use SpamAssassin and don’t have a registered SpamCop account you’ll want to do the same.