If you connect to Outlook via a Mac email client and your organization requires a fresh login after a certain number of days set by its security policy, you might find yourself mysteriously stymied and be unable to troubleshoot the problem if you hit the same snag I did recently.
After years of receiving weekly requests to perform a login and two-factor authentication via my browser for an Outlook account, it suddenly failed. No amount of troubleshooting seemed to allow me to reconnect. Strangely, on a different Mac, authentication continued to work without a hitch.
After a substantial amount of trial and error, I discovered a new piece of software that I had installed interfered with my email client’s browser launch. The new software, PeakHour, operates a tiny local web server to manage some information gathering about your Mac’s data usage. As with all internet-based servers, it requires a port number–a unique number that identifies a particular service on any internet-connected device, like email, secure web browser, and the like.
In trying to troubleshoot an unrelated network problem, I had installed PeakHour, which enabled its server at port 8000. What I didn’t realize (and you can’t find documented anywhere) is that either Outlook or some email client use port 8000 to create a short-lived local web server to manage the authentication with Microsoft’s Outlook login systems. Because my email client couldn’t launch a web page at port 8000–the PeakHour page came up instead–it failed to authenticate.
Most software that creates a local web server also has the option to change the number. I changed it from 8000 to 8002, restarted PeakHour, and was immediately able to get my Outlook email account working again. Check the settings for the software for such an option.
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Author: Glenn Fleishman, Senior Contributor
Glenn Fleishman’s most recent books include Take Control of iOS and iPadOS Privacy and Security, Take Control of Calendar and Reminders, and Take Control of Securing Your Mac. In his spare time, he writes about printing and type history. He’s a senior contributor to Macworld, where he writes Mac 911.