[yabones]

Exchange online is down down. All the MX records are returning SERVFAIL, so something has gone quite badly on MS's side. It could be load shedding, or their authoritative DNS has blown up.

IMAP seems to also be having some sort of problem... Thunderbird has been stuck at "Looking up outlook.office365.com..." for a while.

[observationist]

It's spreading - just hit us about 20 minutes ago, and it's creeping outward. DNS went kablooie - someone's having a horrible day.