Preview build — Pull Request #59

Nested app authentication (NAA) and deprecation of Exchange legacy tokens

Learn how Exchange legacy token deprecation affects Signature 365 and choose between upgrading to NAA, granting permissions, or re-enabling tokens.

Microsoft has launched a new method for Outlook add-in authentication called nested app authentication (NAA). NAA replaces the current authentication method, which Microsoft now refers to as "legacy tokens".

Caution
Microsoft completed disabling of legacy tokens in October 2025

To ensure the Signature 365 add-in continues to work, you have the following options:

  • Upgrade the add-in to version 3.1 - preferred option
  • Continue using the current add-in version manually granting new required permissions

We strongly recommend all customers upgrade the add-in to version 3.1

This will ensure that you are using the latest version of the add-in, and are able to take advantage of the newest updates and features.

As part of this process you will be asked to grant admin consent to two new permissions ("Maintain access to data you have given it access to" and "Sign in and read user profile"). This does not grant Signature 365 any additional access to data but is required for NAA to work.

Updating the Signature 365 modern add-in: Signature 365 Help Center