Outlook errors “Not Implemented” when Reply All to email on ARM devices

Last Updated: April 8, 2022

ISSUE

When a user responds to any email with the Reply All option or by accepting a meeting invite, they receive the error message: “Not implemented”.

This issue is scoped to users on ARM chip architecture.

STATUS: INVESTIGATING/WORKAROUND

The Outlook Team is investigating this issue for a fix. 

To work around this issue, uninstall 32-Bit Office and install 64-Bit Office. 

To confirm the bitness of Office from Outlook:

1. Select File, then Office Account.

2. Select About Outlook and at the top of the dialog.

For more information, see:

• Uninstall Office from a PC

• Download and install or reinstall Microsoft 365 or Office 2021 on a PC or Mac