Tuesday, June 24, 2014, 16:18

Outlook 365 Outage Resolved

Microsoft appears to have resolved the Outlook 365 problem that plagued many mail servers yesterday.

According to the Washington Post: Microsoft users at businesses across the country are reporting a widespread, ongoing outage of their e-mail service that has lasted for much of Tuesday. Some users say that they have seen their service restored this afternoon. (http://www.washingtonpost.com/blogs/the-switch/wp/2014/06/24/microsoft-outlook-outage-reported-across-much-of-the-country/)

We had been experiencing severe email delivery delays sending to Outlook 365 hosted mail domains. When reviewing the PerfectMail Mail Queue you may have seen many messages with the following error status:

421 4.3.2 The maximum number of concurrent server connections has exceeded a limit, closing transmission channel

The Outlook 365 servers appeared to be throttling all incoming email, or there may have been a sudden drop in the connection limit, or there may be some other issue. We had seen many errors connecting to various subdomains within mail.protection.outlook.com. Since this problem had been occuring most of the working day there may have been a more serious issue.

The impact of this issue appeared to affect all email providers sending to Outlook 365 hosted mail domains. If a domain you were sending to had the above error message it is likely hosted on Outlook 365.

As of 6PM ET on Jun 24, 2014, Microsoft confirms that it has resolved the e-mail issue. At this time, the company has not provided details on how many users were affected or on what caused the outage.

The problem now appears to have been resolved and all PerfectMail servers will have cleared their outgoing mail queues.

-- David Rutherford