Scenario
You wish to continue to use legacy tokens in Exchange Online because you need more time to upgrade the Signature 365 add-in.
CAUTION
Legacy tokens will be disabled by Microsoft in June 2025. This method should only be used as a temporary measure to allow more time to upgrade the add-in to version 3.0 or grant the required permissions for earlier versions.
Solution
- Open PowerShell on your device
- Run the following cmdlet and sign in with your Microsoft 365 administrator credentials:
Connect-ExchangeOnline
- Run the following cmdlet to enable legacy tokens:
Set-AuthenticationPolicy –AllowLegacyExchangeTokens -Identity "LegacyExchangeTokens"
The command will return "Success"
You can confirm this has been successfully completed by running the following cmdlet:
Get-AuthenticationPolicy -AllowLegacyExchangeTokens
This cmdlet will return the following if successful:
AllowLegacyExchangeTokens: True
For more information on the ability to enable and disable Exchange Online legacy tokens, please see the following Microsoft article:
Turn legacy Exchange Online tokens on or off - Office Add-ins | Microsoft Learn