Global email is currently being disrupted because Cisco has let Spamcop.net expire. We saw an issue in our logs this am as all emails from known non-spammers were being flagged. Our servers were checking bl.spamcop.net. We also saw that the “service was unavailable” which was when we discovered the domain had expired. We thought it was mistake but then others started reporting the same.
SpamCop is one of the widely used DNS blacklist providers on the Internet. It looks like someone has the domain parked now so this may be a bit slow to resolve.
So there you have it. Your emails are not being delivered because Cisco was asleep at the switch. The bigger the company, the bigger and slower the bureaucracy.
What to do: If you run your own mail server, remove blacklist checks against bl.spamcop.net. If you do not, contact your ISP.
Monday will not be fun!