Here are the prerequisites for installing and using the Letsignit add-in.

  • Available only for Microsoft O365 customers

    • No limit on number of users

    • Simultaneous deployment on OWA and Outlook desktop

    • Using Outlook with a Microsoft 365 subscription

      • Outlook must be installed with the license included in your O365 subscription

      • Some Microsoft subscriptions do not include Outlook desktop (the Basic licence for instance)/

  • O365 messaging only

  • Available on Windows and MAC

Which O365 license is compatible with the add-in?

  • Microsoft 365 Apps for Business

  • Microsoft 365 Business Standard

  • Microsoft 365 Business Premium

The Microsoft 365 Business Basic license will only allow you to deploy the add-in on the web mail.

How do I know my Outlook license?

  1. On Outlook (Windows)

    • Go to File > Office Account

    • The name of your license will be displayed under "Product Information" on the right side of the window.

  2. On your O365 admin console

    • In the Billing > Your Products section


    • In the Users > Active Users section



Minimum Windows version required

Event-based add-ins in Outlook on Windows require a minimum of Windows 10 version 1903 or Windows Server 2019 version 1903 to run.

Minimum Outlook version required by update channel :

  • For users on the current channel: v16.0.14026.20000

  • For users on the monthly channel: v16.0.14131.20000

  • For users on the semi annual channel: v16.0.14326.10000

How to know your M365 update channel?

In Outlook desktop, click on File / Office Account / About

How to know the version of your Outlook Windows?

In Outlook desktop, click on File / Account Office / About


  • Compatible only with the new version of Outlook

How to activate the new version of Outlook for MAC?

1/ Activate the new Outlook version via the toogle on the top right

2/ Click on "Open the new Outlook", Outlook will automatically restart with the new version

  • Minimum Outlook version required: 16.54 (21101001)

How to know the version of your Outlook MAC?

Click on Outlook menu at the top left, click on "About Outlook".

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