Microsoft rolls out fix for New Outlook attachment failures

Microsoft is rolling out a fix for a fault that prevents some New Outlook desktop users from opening email attachments. The company said an update to its Edge browser, version 156, unintentionally enabled an “unnecessary configuration,” as The Register described on October 29.

Microsoft acknowledged the problem on October 28 in advisory EX1528992. The advisory records the incident’s start as 17:24 CET that day and identifies the affected group as New Outlook desktop users who upgraded to Edge 156. Microsoft has not given a count of affected users.

How to open attachments while the fix rolls out

Some affected users see an error saying the file cannot be opened and telling them to restart Outlook. After that error, the attachment’s Open option disappears.

Microsoft’s workaround is to select Save As to download the attachment, then open the saved file manually. Classic Outlook appears unaffected, based on Microsoft’s advisory; that assessment is not a guarantee for every user.

Deployment needs confirmation, then an app restart

In its October 29 update at 02:05 CET, Microsoft said it had developed and deployed a targeted fix to disable the configuration. It said the change could take up to 12 hours to reach all its service systems. Microsoft has not explained what the configuration does.

As of 10:55 UTC on October 29, Microsoft had not confirmed full restoration, and the incident remained listed as a service degradation. The company said it would use service telemetry—operational data from its systems—to confirm that the fix had reached its infrastructure. Once Microsoft confirms deployment, users must close and reopen New Outlook for the change to take effect.