Enable legacy Exchange Online tokens

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