By Sergiu Gatlan
Publication Date: 2025-12-01 17:42:00
Microsoft is working to resolve a known issue that prevents some users from opening Excel email attachments in the new Outlook client.
According to a service alert (EX1189359) seen by BleepingComputer, the bug has been impacting Exchange Online customers since at least November 23rd.
Microsoft says it has already deployed a fix to address the bug and added that the root cause is an encoding error in Excel file names, which triggers a “Try opening the file again later.” error for affected users.
While Microsoft also noted that this issue may affect any user who attempts to open attachments with non-ASCII characters in the name, it has not yet provided more details on the extent of the problem.
However, this incident has already been tagged as an advisory, a label commonly used to describe service issues typically involving limited scope or impact.
“Any user may be unable to open Excel files attached to email messages in the new Outlook client if the attachment…
