With server-side setting, the default email signature is added at the bottom of the email chain.
If reply/forward 'divider' is detected, the reply signature is added above the 'divider'.
The 'divider' is found in Outlook on Windows/Mac and in Outlook on the web (browser).
The result is that the recipients will see the email signature.
The email signature is not visible as the email is composed.
Office 365 environment is required.
Rerouting must be setup before 'Fully server-side' is enabled.
How to setup Rerouting
How to enable 'Fully server-side'
Select 'Fully server-side':