Some Microsoft 365 users have been experiencing issues when sending emails via Outlook, especially those with more than 500 folders in their inbox. The error manifests as a dialog box with the error code 0x80040305, which indicates a “non-delivery report,” meaning that the email fails to reach its intended recipients. This problem has been a source of frustration for many, particularly those managing large amounts of data within Outlook.
Microsoft first acknowledged the issue in early December, but it wasn’t until a September 30th update that developers indicated they had identified the root cause and were working on a solution. The fix is expected to be included in an upcoming update, with Microsoft confirming that a patch would be rolled out soon. This means the problem could soon be resolved for affected users, providing much-needed relief.
Upcoming Patch Targets Outlook Email Issues for Microsoft 365 Users with Over 500 Folders
The update is expected to be available in phases, with Microsoft 365 Insiders getting it first. Those on the Beta Channel should receive the patch in early October, while the final update is scheduled for a broader rollout on October 29th. However, enterprise users may need to wait a bit longer, as the patch for them is slated for release on December 10th.
For those who are currently impacted by the bug and cannot wait for the official fix, there are some temporary workarounds. Microsoft suggests reducing the number of folders in the inbox to under 450 and recommends collapsing any folders that contain large amounts of data. These steps may help mitigate the issue until the update is officially deployed.
