Introduction

What is an Add-in.
An Outlook add-in is a small extension that runs inside Microsoft Outlook to provide extra features beyond the standard email, calendar, and contacts functionality. It integrates directly into the Outlook interface, so users can access additional tools without leaving their inbox. Technically, an Outlook add-in is a web-based application defined by a manifest that describes how it plugs into Outlook and supported scenarios, plus HTML, JavaScript, and related resources that implement its logic and user interface. Because it uses web technologies and Microsoft’s add-in platform, the same solution can usually run across Outlook on Windows, Mac, web, and mobile with a single codebase. Outlook add-ins connect to external services to do tasks such as inserting email signatures. Users and administrators can acquire them from the Microsoft commercial marketplace or deploy them centrally, making them a flexible way to tailor Outlook to specific business processes.

At the heart of these services is a new cloud-based API layer that DynamicSignature exposes to its customers. Once the add-in is deployed to your tenant, Outlook is configured to bypass its built‑in signature functionality and instead rely on the add‑in’s own signature logic. From that point on, all signatures are retrieved from the API rather than from local Outlook storage.

This is how the new Add-in looks like in Outlook accross the different platforms.