MF sent two reports of emails that were rejected. The first appears to be a case where the user submitted an erroneous return email address, and our system eventually gave up trying and reported that failure.

The second appears to be a case of someone spoofing the admin@ and webmaster@ accounts and somehow getting those addresses put on a blacklist somewhere. It seems to be a pretty localized thing, as I have no other problem reports (which I'd expect if suddenly those accounts were universally blacklisted, or suspended by the sys-admins)