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.
The Outlook Add-in is only supported for Outlook 365 subscription versions due to limitiations from Microsoft.
If you are using perpetually licenced versions of Outlook (2016 / 2019 / 2021) you will need to use the Outlook Agent following the instructions here: How to install the Outlook (Classic) agent : Signature 365 Help Center
The addin can be deployed from the Microsoft 365 Admin center to apply to users, group or your entire organisation, or it can be installed from the "Get Addins" option in Office 365 for individual users or testing purposes.
Please note that the Outlook add-in must be deployed to your users using one of these two methods. If the add-in is installed manually by a user from the Add-in store, it will be unable to insert signatures due to a security limitation imposed by Microsoft.
In the Outlook menu ribbon, click the Get Add-ins button.
In the Add-ins window that opens, select My add-ins, and scroll down until you see the Custom Addins section.
Click + Add a custom add-in and in the dropdown that appears select the Add from URL... option.
In the pane that opens, enter https://outlook.signature365.com/manifest.xml for the URL of the manifest file.
Review the warning and Select Install.
The Signature 365 addin will appear in the Custom Addins section, and will now be available when composing a new message.
Log on to the Microsoft 365 Admin center as a Global Administrator.
Go to Settings > Integrated apps to open the Integrated apps page, and click Get Apps to open the AppSource pane.
Enter Symprex Signature 365 into the search box, and click the Get it now button.
Click Get it now to confirm and continue.
This will direct you to the Microsoft 365 Admin center to deploy the Signature 365 for Outlook add-in and choose the users you want to assign the add-in to.
You can change this option later and/or edit any specific users/groups you initially choose. Note that when selecting the Specific users/groups option, this will by default send the users an email notification unless you disable this option.
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 Done to close the add-in pane.
The add-in is now visible in the Microsoft 365 Admin center and will deploy to your selected users.