Starting with version 1.1 of the schema for Office Add-ins manifests and v1.1 of office.js, you can create compose add-ins, which are Outlook add-ins activated in compose forms. In contrast with read add-ins (Outlook add-ins that are activated in read mode when a user is viewing a message or appointment), compose add-ins are available in the following user scenarios:
Composing a new message, meeting request, or appointment in a compose form.
Viewing or editing an existing appointment, or meeting item in which the user is the organizer.
Note If the user is on the RTM release of Outlook 2013 and Exchange 2013 and is viewing a meeting item organized by the user, the user can find read add-ins available. Starting in the Office 2013 SP1 release, there's a change such that in the same scenario, only compose add-ins can activate and be available.
Composing an inline response message or replying to a message in a separate compose form.
Editing a response ( Accept, Tentative, or Decline) to a meeting request or meeting item.
Proposing a new time for a meeting item.
Forwarding or replying to a meeting request or meeting item.
In each of these compose scenarios, any add-in command buttons defined by the add-in are shown. For older add-ins that do not implement add-in commands, users can choose Office Add-ins in the ribbon to open the add-in selection pane, and then choose and start a compose add-in. The following figure shows add-in commands in a compose form.
The following figure shows the add-in selection pane consisting of two compose add-ins that do not implement add-in commands, activated when the user is composing an inline reply in Outlook.
Types of add-ins available in compose mode
Compose add-ins are implemented as Add-in commands for Outlook.
API features available to compose add-ins
For activating add-ins in compose forms, see Table 1 in Specify activation rules in a manifest.