Problem
Users report error when they try to report/block a message using the Outlook Add-In.
Error sample:
| Failed to report this email as spam (Reason: 500 The given header was not found) |
Important:
This workaround described below will stop working on June 1st according to microsoft. Previously the set time for the workaround to work was october but it looks like Microsoft changed their mind at the last minute.
What is the timeline for shutting down legacy Exchange online tokens?
Legacy Exchange online tokens have already been turned off for most tenants. We've provided tooling for administrators to reenable Exchange tokens for tenants and add-ins if those add-ins aren't yet migrated to NAA. For more information, see Can I turn legacy tokens back on?.
| Date | Legacy tokens status |
|---|---|
| Now | Legacy tokens turned off for most tenants. Admins can reenable legacy tokens via PowerShell. |
| Jun 2025 | Legacy tokens turned off for all tenants. Admins can no longer reenable legacy tokens via PowerShell. Admins can request an exception through Microsoft Support at https://aka.ms/LegacyTokensByOctober (this link requires you to sign in to your tenant). |
| Oct 2025 | Legacy tokens turned off for all tenants. Exceptions are no longer allowed. |
Vircom is working on a solution that we hope will be ready in June ... in the meantime, the only recourse would be to request an exception from microsoft from within the Office365 tenant of the client
Solution [Probably deprecated as of June 1st 2025]
The issue is that the plugin uses Exchange Tokens that will be deprecated in 2025. Microsoft has already turned on deprecation but in the meantime, you can override the deprecation by enabling the legacy Exchange Tokens via a powershell script.
You need to do this with Global Admin credentials for the entire O365 tenant. This needs to be done *before* June 2025. Script can be run on any machine.
WINDOWS 10
Open the PowerShell (admin mode) prompt and run the following commands:
- Set-ExecutionPolicy RemoteSigned
- Install-Module -Name ExchangeOnlineManagement
- Update-Module -Name ExchangeOnlineManagement
- Connect-ExchangeOnline
- Set-AuthenticationPolicy –AllowLegacyExchangeTokens -Identity "LegacyExchangeTokens"
WINDOWS 11 / SERVER 2022
Still in QA - Will update the KB once confirmed
NOTE: The powershell command doesn't run on windows 11 for some reason but runs on windows 10 ... however it will fix it for everyone using the plugin so just run the script on a win10 box and it'll fix the issue for all users
It can takes up to 24 hours for Microsoft to proceed with the re-activation.