Hosts - ExtensionPoint

<VersionOverrides> 
   <Hosts> 
      <Host xsi:type="Workbook"> 
         <DesktopFormFactor> 
            <ExtensionPoint xsi:type="PrimaryCommandSurface"> 

Hosts - ExtensionPoint - CommandSurface

Commands

PrimaryCommandSurface
The ribbon at the top.

<ExtensionPoint xsi:type="PrimaryCommandSurface"> 

MessageReadCommandSurface
The mail read view task pane window

<ExtensionPoint xsi:type="MessageReadCommandSurface"> 

MessageComposeCommandSurface
The mail compose form task pane window

<ExtensionPoint xsi:type="MessageComposeCommandSurface"> 

AppointmentOrganizerCommandSurface

<ExtensionPoint xsi:type="AppointmentOrganizerCommandSurface"> 

AppointmentAttendeeCommandSurface

<ExtensionPoint xsi:type="AppointmentAttendeeCommandSurface"> 

MobileMessageReadCommandSurface

<ExtensionPoint xsi:type="MobileMessageReadCommandSurface"> 

MobileOnlineMeetingCommandSurface

<ExtensionPoint xsi:type="MobileOnlineMeetingCommandSurface"> 

Hosts - ExtensionPoint - ContextMenu

ContextMenu

<ExtensionPoint xsi:type="ContextMenu"> 
<OfficeMenu id="ContextMenuCell"> 
   <Control xsi:type="Menu"> 

Hosts - ExtensionPoint - CustomFunctions

Custom Functions

<Hosts> 
<Host xsi:type="Workbook"> 
<AllFormFactors> 
<ExtensionPoint xsi:type="CustomFunctions"> 
   <Script> 
   <Page> 
   <Metadata> 
   <Namespace resid="short_string_id"> 

Hosts - ExtensionPoint - CustomPane

<ExtensionPoint xsi:type="CustomPane"> 

SourceLocation - Required. The URL for the source code file of the add-in. This refers to a Url element in the Resources element.
Rule - Required. The rule or collection of rules that specify when the add-in activates. It is the same as defined in Outlook add-in manifests, except the ItemIs rule has the following changes: ItemType is either "Message" or "AppointmentAttendee", and there is no FormType attribute. For more information, see Custom pane Outlook add-ins and Activation rules for Outlook add-ins.
RequestedHeight - Optional. The requested height, in pixels, for the display pane when it is running on a desktop computer. This can be from 32 to 450 pixels. It is the same as in read add-ins (see RequestedHeight element (ItemReadTabletMailAppSettings complexType) (app manifest schema v1.1)
DisableEntityHighlighting - Optional. Specifies whether entity highlighting should be turned off for this mail add-in.

Hosts - ExtensionPoint - DetectedEntity

Outlook only (Added 1.6)
Add a contextual add-in activation specific entity type for a
Registering mailbox and Item events is not available on this extension point.

<ExtensionPoint xsi:type = "DetectedEntity"> 
  <Label resid="residLabelName"/> 
  <RequestedHeight>300</RequestedHeight> 
  <SourceLocation resid="residDetectedEntityURL"/> 
  <Rule xsi:type="RuleCollection" mode="And"> 
    <Rule xsi:type="ItemIs" 
          ItemType="Message"/> 
    <Rule xsi:type="ItemHasKnownEntity" 
          EntityType="MeetingSuggestion"/> 
          Highlight="all"/> 
    <Rule xsi:type="ItemHasRegularExpressionMatch" 
          RegExName="BetterCode" 
          RegExValue="BET-\d{a}" 
          PropertyName="BodyAsPlaintext"/> 
  </Rule> 
</ExtensionPoint> 

Label -
RequestedHeight -
SourceLocation -
Rule -

Hosts - ExtensionPoint - Events

Outlook only

<ExtensionPoint xsi:type = "Events"> 
  <Event Type="ItemSend" 
         FunctionExecution="synchronous" 
         FunctionName="validateEmailBody" 
  </Event> 
</ExtensionPoint> 

Hosts - ExtensionPoint - LaunchEvent

Outlook only
Enables an add-in to be activated based on supported events in the desktop form factor.
Event Based Activation

<ExtensionPoint xsi:type = "LaunchEvent"> 
  <LaunchEvents> 
    <LaunchEvent Type:="OnNewMessageCompose" 
                 FunctionName="onNewMessageHandler" 
    </LaunchEvent> 
    <LaunchEvent Type:="OnNewAppointmentOrganizer" 
                 FunctionName="onNewAppointmentHandler" 
    </LaunchEvent> 
  </LaunchEvents> 
  <SourceLocation resid="WebViewRuntime.Url"/> 
</ExtensionPoint> 

Hosts - ExtensionPoint - Module

Outlook only
Extension Modules lets you create new modules inside Outlook

<DesktopFormFactor> 
<ExtensionPoint xsi:type = "Module"> 
   <SourceLocation> 
   <Label> 
   <CommandSurface> 
      <Control xsi:type="Button" 
               id="custombutton"> 
      <Label> 
      <Action xsi:type="ExecuteFunction"> 
          <FunctionName> 
      </Action>