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What are the pre-requisites to benefit from the Add in ?
What are the pre-requisites to benefit from the Add in ?
Stephanie avatar
Written by Stephanie
Updated this week

Take advantage of our New Addin for free - Included in your current offer

  • Available on Windows and MAC

  • Simultaneous deployment on OWA, Outlook Desktop and mobile iOS and Android

  • Also compatible with the new One Outlook

Prerequisites for installing and using the Letsignit Add-in.

Subscriptions and licenses

  • Letsignit Add-in is only available to users with a Microsoft 365 subscription.

Outlook must be installed with the license included in your M365 subscription (please note that some Microsoft subscriptions do not include Outlook Desktop).

  • Compatible O365 licences

  • Microsoft 365 Apps for Business

  • Microsoft 365 Business Standard

  • Microsoft 365 Business Premium

  • Microsoft 365 E3, E5, F3

Please note that the Microsoft 365 Business Basic license will only allow you to deploy the Add-in on webmail (OWA): https://www.microsoft.com/fr-fr/microsoft-365/business/compare-all-microsoft-365-business-products


On Windows

Minimum Outlook version required, depending on 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 ?

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


On Mac OS

  • Compatible only via Outlook's new UI on Mac

Minimum 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".

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


Proxy permissions

If your local network includes a proxy to filter and secure your internet requests, it is necessary to allow the following 2 URLs to be output for the Add-in to work properly:

Note that depending on the type of proxy (McAfee Web Gateway for example), it may be necessary to set this syntax:

  • *storage.letsignit.com*

  • *aladin.letsignit.com*

It is necessary to test the Add-in if your security does 'Man-In-The-Middle' and/or SSL decryption and/or Java inspection because the requests are formatted with a certificate to Letsignit infrastructures.

If you find that you cannot connect or that the add-in does not insert signatures, this may be the case.


The proper functioning of the Letsignit Add-in can sometimes be impacted if other Add-ins are deployed to a user. This is often the case with spell checkers or dictionaries.

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