Pieter van der Westhuizen

Outlook 2016 Extensibility

The Office 2016 release is upon us and it is time we start having a closer look at the new features and changes in Outlook as well as what new extensibility the new Office 2016 platform offers to Outlook developers.

Outlook 2016 UI / usability changes

The most noticeable changes in the Microsoft Outlook 2016 user interface are as follows.

New theme

The most obvious change you’ll notice in Outlook 2016 is the new color scheme. The default theme is called “Colorful” and changes the title bar/header of Outlook to a blue color to fit in with the new modern apps for Windows.

New color scheme of Outlook 2016

Tell Me

Tell Me is an interesting new feature in Outlook 2016 that saves the user time by allowing them to search for something directly from either the Explorer or Inspector ribbons. For example, in the following screenshot, I wanted to show the BCC Field and all I had to do was type “bcc” in the Tell Me search box. It would be interesting to see if Microsoft will provide some sort of extensibility for the search box in order for Outlook developers to add their own search terms and functionality to Tell Me.

The Tell Me feature in Outlook 2016

Email attachments

Attaching files to emails now presents the user with a list of recently used items instead of the traditional “Browse for file” dialog window we’ve come to know over the years. You’ll notice the list also contains a “Browse Web Locations” option which provides you with the ability to attach files from services like OneDrive directly to your email – a nice idea!

Email attachment changes in Outlook 2016

The Clutter folder

Although not entirely new to Outlook 2016, I’ve also noticed the Clutter folder that was added to my Outlook 2013 (this is probably because I use Office 365 Exchange). The Clutter folder’s aim is to help you focus on important messages by automatically moving low priority messages to the Clutter folder. In a way it reminds me of the Gmail tabs that automatically sort similar mails.

The Clutter functionality examines what you’ve done in the past to determine which messages to move. It is a nice touch and something I’m sure Microsoft will build upon in the future.

The Clutter folder in Outlook 2016

Outlook 2016 extensibility changes

Apps for Office and Apps for SharePoint have been rebranded as Office Add-ins and SharePoint Add-ins. This can cause some confusion as we’ve always referred to the classic COM / Managed Office add-ins as “add-ins” and the new JavaScript/HTML Office Apps as “apps”.

Both these technologies are now referred to as “Office Add-ins”, although we’ll still refer to the traditional COM based add-ins as “COM / Managed Add-ins”.

COM / Managed add-ins

Microsoft is aggressively pushing the new Office JS extensibility model which allows developers to write integrations for MS Office using web technologies such as JavaScript and HTML. This does, however, not mean that COM/Managed Add-ins are going anywhere.

The new object model, although improved significantly, still does not provide most of the features and abilities that traditional COM/Managed Add-ins offer developers, such as advanced regions and events.

As always, Add-in Express still has you covered with regard to COM/Managed Add-ins, as our latest version supports all versions and editions of Microsoft Outlook stretching from 2000 right up to 2016. That’s right, Add-in Express for Office is the only toolset that allows you to support 15 years of MS Office with one codebase!

Add-in Express for Office and .net allows you to support all versions of Office 2000 to Office 2016 with one codebase

Napa Cloud App

In the past when you wanted to create an Office Add-in using the Office Napa tools you needed to have a SharePoint site collection tied to your Napa account.

This requirement has been removed, meaning even if you do not have a SharePoint site collection on Office 365, you can still create Office Add-ins using the web based editor provided by Napa, by simply signing into Napa using your Microsoft account. This is intended to get developers involved in developing Office add-ins without the need for any additional services such as SharePoint.

Add-in commands

Add-in commands are a new feature added to the OfficeJS library. It allows developers to add ribbon buttons to the Outlook 2016 ribbon that can:

  • Show a task pane
  • Execute a JavaScript function
  • Show a dropdown with additional options

This is a big step from the previous version of OfficeJS, as it was a little trickier to show your Add-in task pane since your Add-in was hidden behind the Office Apps button that showed the user a list of available apps to run.

Add-in commands are supported for the following:

  • Mail Message Read
  • Mail Message Compose
  • Calendar Event Organizer
  • Calendar Event Attendee

This feature brings your app to the front and allows developers to also execute functions without having to show a UI. This is certainly a step in the right direction with regard to Office Apps written with JavaScript and HTML.

Office UI Fabric

Office Fabric is Microsoft’s mobile-first, responsive, front-end framework for creating Office Add-ins using JavaScript, CSS and HTML. If you’re familiar with web frameworks such as Twitter Bootstrap or Foundation, you’ll be comfortable with using Office Fabric.

It is intended to help you create native looking Office apps since Fabric embodies the Microsoft Design Language. It provides ready to use components, styled to fix in perfectly with Office, such as a Dialogs, callouts and buttons.

You can read more about Office UI Fabric and get the latest source code on GitHub.

Cross-platform add-ins

Earlier this year, Microsoft announced at their BUILD conference that Office for Mac will support Office Add-ins in the future. They’ve also announced the same support for their Office version for Android and iOS.

All of this is of course due to the fact that Office Add-in was created using web technologies like JavaScript, CSS and HTML. This is great news for Office developers, as it will allow us to target Office users that were previously out of reach.

Another exciting result of this is you can now also built Office Add-in for Office on the iPad!


As you can see Microsoft is actively enhancing and improving their Office platform for developers, be it via OfficeJS or their Office 365 APIs. Things are changing fast and new and grand opportunities are available for Office developers on a regular basis. It is an exciting time to be an Office developer.

We’ll take a closer look at creating Office Add-ins using HTML, CSS and JavaScript in future blog posts, so please keep watching this space.

Thank you for reading. Until next time, keep coding!


  • Fabske says:

    Nice article, but you didn’t explain any changes for the COM / Managed add-ins?

  • Simon says:

    When will we be able to download the updated Add-In Express product that office Office 2016 COM creation ?

  • Jon says:

    With the new Colorful and Dark Therese, there is a need to include both Dark and Light versions of custom icons and to switch between them on the quick access toolbar when the theme is changed. The built-in Office icons do this. Is there a way to do it with ads-in icons?

  • Pieter van der Westhuizen says:

    Hi Fabske,

    From what I could gather there was not any changes with regards to COM/Managed add-ins in the new release of Office.

  • Pieter van der Westhuizen says:

    Hi Jon,

    There does not appear to be an easy way to do this. However, you can maybe include icons for each color scheme and follow the approach described in Eugene and Dmitry‘s articles.

  • Dmitry Kostochko (Add-in Express Team) says:

    Hi Simon,

    We plan to publish the release version of the Add-in Express for Office and .net product in October.

  • Simon says:

    Thanks Dmitry. Very much looking forward to it. Considering I have several projects build as Office 2013 COM (with the wizard) will there be a way to make the projects 2016 compatible without a complete project rebuild ?

  • Dmitry Kostochko (Add-in Express Team) says:

    Hi Simon,

    You will need to install Add-in Express V8, compile your projects and test them in Office 2016 applications.

  • Brain2000 says:

    Do you know when the Addin Express version 8 download will no longer be labeled as a beta?

  • Andrei Smolin (Add-in Express Team) says:


    We plan to release a new version of Add-in Express in 2-3 weeks starting from September 22nd. We need to test it with the release version of Office 2016. I’ll post a note here when the new version is released.

  • Andrei Smolin (Add-in Express Team) says:


    We’ve published Add-in Express version 8 (build 8.0.4330). Please download it at https://www.add-in-express.com/downloads/adxnet.php.

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