From Microsoft Health Dashboard:
The BPOS Operations team is working to resolve service degradation for Exchange Online mail flow for organizations served from this region. Users in affected organizations will experiencing ~40 minute delays when trying to send or receive e-mail using Outlook, OWA, or mobile devices. The BPOS Operations team is actively working to restore service. Next update will be within one hour or when new information is available.
Not sure about anyone else, but ~40 minutes is off by about infinity for me.
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Two days in a row now, and if you were watching Twitter it would appear to be affecting a lot of people in the NOAM region. Oddly, the Health dashboard still doesn't show a problem:
Try calling MS support though, it will just hang up on you.