Classic Outlook is also fired from Teams connection

A bug in the interaction of Microsoft software is currently making the classic email client Microsoft Outlook completely unusable for some users. The cause appears to be a plugin connection to Teams.

Update can help

Users who have activated the Teams meeting add-in are particularly affected. The issue was confirmed by Microsoft in an update in the Admin Center. Accordingly, Outlook cannot be used properly in the classic version if the Teams add-in is active. The company has not yet given any specific details about the technical cause, but pointed out that an older version of Outlook was responsible for the problem. Users who are not yet working with the latest version are particularly susceptible to the problems.

As a temporary solution, Microsoft recommends updating Outlook to the latest version. Alternatively, one could Online repair for click-to-run installations, in which all Office applications are reinstalled. This is to ensure that the current version of Outlook is being used and the error no longer occurs.

Solution in progress

At the same time, Microsoft is investigating further problems related to Outlook. Users report connection problems when synchronizing with external email services such as Gmail and Yahoo Mail. Among other things, the error codes 0x800CCC0F and 0x80070057 occur, which indicate difficulties in data transfer. Microsoft has already had to struggle with similar problems in recent months. In January, a bug was fixed that caused encrypted emails to no longer open in Outlook following updates in December 2025.

The company also had to contain a large-scale disruption at Exchange Online earlier this week. This resulted in numerous customers not having access to their mailboxes and calendars – regardless of whether they used Outlook on the web, on the desktop or via mobile synchronization protocols. Microsoft says it is still working on a permanent solution to the current Outlook problems.