By Guru Baran
Publication Date: 2025-12-01 18:07:00
Microsoft has acknowledged a frustrating new issue affecting users of the “new Outlook” for Windows, where Excel attachments fail to open if their filenames contain non-ASCII characters.
The technical glitch, tracked under the reference ID EX1189359, triggers a vague error message advising users to “Try opening the file again later,” leaving many confused about the cause of the blockage.
The problem targets the modern “new Outlook” client explicitly and does not appear to impact the classic version of the software. According to Microsoft’s service health dashboard, the root cause lies in an encoding error within the request used to open the files.
When an Excel file attached to an email includes non-standard characters such as accented letters, symbols, or non-English scripts, the application fails to process the filename correctly, resulting in an immediate error.
This issue has been ongoing since late November 2025, with…