Exchange Online went offline earlier Tuesday, affecting businesses that had shifted to the off-premises email service, either as a stand-alone or as part of their move to the Office 365 "rent-not-own" subscription programs that the company has been aggressively pushing.
Reports of problems accessing email via Exchange Online -- the off-premises service bundled with most Office 365 business plans -- began appearing shortly before 10 a.m. Eastern time, (7 a.m. Pacific time), as users signed in and realized that mail wasn't appearing in their in-boxes.
Microsoft confirmed the outage later in the morning.
"Some Exchange customers are experiencing email delays," a spokeswoman said in an email reply to questions. "Our engineering team is actively working to resolve this issue. We recommend customers visit the service health dashboard for real-time updates."
The Exchange Online outage followed a similar Lync blackout yesterday. Lync is Microsoft's server-based software that provides instant messaging, Internet calling and videoconferencing services to enterprises.
Computerworld and other IDG publications and divisions were among those affected by the Exchange Online outage.
Customers weren't happy, and they took to Twitter -- not surprising, since they were bereft of email -- to by turns mock Microsoft and complain about the service.
"#office365 is down. Should we now call it #office364?" asked Molly Urciolo of the Washington Post.
"Microsoft, have you tried turning it off and on again? #Office365 outage," tweeted Adam Zaimes.
"This might be the worst day ever for using Exchange Online. Down since 8:30am central with no ETA to return to service," chimed in Josh Widup.
"How annoying is it to get an @office365 twitter ad when the service has been dead for 5 hours!?" asked Phil Wiser, CTO of Hearst Corp., the newspaper and magazine publisher and owner of a string of U.S. television stations.
Even as the outage struck, however, customers reported that their Office 365 service health dashboards had not reported issues.
"This is pathetic," someone identified as ISTE_IT wrote in a fast-growing thread on Microsoft's support forum. "Microsoft should consider that an outage like this, a day after the Lync outage, is a black mark that will cost you customers."
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter, at @gkeizer, and on Google+, or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.