Microsoft is adding .msix and .msixbundle files to the blocked attachment list in Outlook on the web and the new Outlook for Windows, with the Exchange Online rollout starting in early November 2026 ...

Say goodbye to .msix and .msixbundle files in your email (unless your admin whitelists them).

Microsoft announced that it will add .msix and .msixbundle attachments to the list of blocked attachments in Outlook Web and the new Outlook Windows client starting next month.

New Outlook for Windows and Outlook on the web will block .msix app package attachments by default from November.

There are various file types which can be abused by threat actors if sent as email attachment. Because of these risks, there are blocks on sending such files attached to emails, and Microsoft has just ...