Outlook users around the world were experiencing issues with vanishing emails today (May 11) with Microsoft confirming it is investigating the issue -- which unusually seems to be affecting the client app directly.
The bug appears to have been introduced with Outlook version 2104 build 13929.20372, released today for the desktop client. Reverting the build seems to fix the issue, according to multiple users.
(e.g. run C:\Program Files\Common Files\microsoft shared\ClickToRun\OfficeC2RClient.exe" /update user updatetoversion=16.0.13901.20462)
"I can read the text of messages sent to me, but when I reply the text disappears and I'm unable to see the original message or my own typing" one user wrote. Others -- from the UK to NZ -- reported the same bug. "We’re investigating an issue with email message visibility in Outlook. Outlook on the web appears to be unaffected" Microsoft said.
The issue comes just a day after numerous EMEA users saw emails randomly quarantined, with Microsoft admitting it was "investigating an issue with email flow, links within email messages and the Microsoft Defender portal" before ultimately mitigating around 19:30 BST.
Microsoft's had a torrid run on uptime and buggy updates in recent months -- including with ongoing issues around its crypto key rotation system, which caused proctracted outages in March 2021 and September 2020.
In March Microsoft said it Azure AD is in a “multi-phase effort to apply additional protections to the backend Safe Deployment Process (SDP) system to prevent a class of risks including this problem”, adding “we understand how incredibly impactful and unacceptable this is”.
Microsoft said 22:18pm BST it is "investigating data to isolate the root cause".