The Signature 365 add-in for Outlook allows users to preview signatures, add signatures to email so they appear directly below the email being composed, and to select an alternative signature if additional signatures have been assigned to them.
How to deploy add-in from the Microsoft 365 Admin center
Log on to the Microsoft 365 Admin center as a Global Administrator.
Go to Settings > Integrated apps to open the Integrated apps page:
Click Upload custom apps to open the Upload Apps to deploy pane:
Select the Provide link to manifest file option and enter this URL:
Make sure to include the https:// protocol specifier in the URL:
Click Validate to validate the manifest file:
Click Next to continue to add users:
Choose the users you want to assign the Signature 365 Outlook add-in to. You can change this option later and/or edit any specific users/groups you initially choose:
If you select the Specific users/groups option, Microsoft 365 will only deploy the add-in to users that are direct members of any groups you specify. Members of any nested groups will not be included. This is a limitation of Microsoft 365.
Click Next to continue to review permissions:
Click Next to continue to review and finish deployment:
Click Finish deployment to deploy the add-in:
It may take a minute for the deployment to complete and the confirmation to show:
The add-in may not be available to all users immediately. The deployment usually only takes a few minutes but can take up to 6 hours according to Microsoft. For some users the add-in may not be available until Outlook has been restarted.
Click Close to close the add-in pane or click Next to learn how to announce the add-in to your users.
The add-in is now visible in the Microsoft 365 Admin center: