OWA add-ins are Outlook integrations developed by the third parties using a new web technologies based platform. It’s not only a modern way to extend Outlook Web Application but also a great way to bring a cross-platform approach to the Outlook add-in development.
OWA add-ins are supported on:
– Outlook 2013 and latest versions
– Outlook 2016 for Mac
– Outlook Web App for Exchange 2013 on-premises
– Outlook Web App in Office 365
– Outlook Web App in Outlook.com
Unlike the old integrations like COM or VSTO, OWA add-ins allow you to use the same source code to run your add-in on all supported platforms. It’s all possible as add-in runs in a browser running in a sandbox rather than the app installed directly on a user PC.
It can be hard to choose the right approach for building an Outlook add-in. So I am going to highlight the main advantages and disadvantages of OWA add-ins which I have identified during the development of both VSTO and OWA add-ins.
– Cross-platform – it’s the biggest advantage of OWA add-ins. There is no more need to develop a few versions of an add-in to support Windows, Mac and Web versions of Outlook. You can build one and use it across all supported devices. Surely there are some limitations as not all platforms support the latest version of OWA add-in functionality but it’s a big step for the future of Outlook integrations development.
– Easy updates. Do you want all of your users to keep using the latest version of your Outlook integrations? Then it is great news for you as you can update your OWA add-in the same way as a usual website. All you need is to update your server and then all users will receive the changes. Below there is an explanation from Microsoft about the interaction of Outlook and OWA add-in.
– Easy acquiring. There are two ways to install your add-in. The first one is to upload add-in to the Office store where a user can enable it by just turning it On.
Also, you can install it by entering the manifest URL manually.
There is no more need to prepare an installation file required to run on all of your customer’s PCs.
– Offline access. There is a need to have access to your web server during add-in execution. It means that Outlook is not possible to run the add-in without access to the web server as it’s possible with VSTO add-ins. So if it’s important for you to keep add-in working in offline then OWA add-ins is not a good solution.
– Auto-launching. In the current implementation of OWA add-ins, it’s not possible to execute the add-in on Outlook start. For example, you can’t keep a task pane opened during email switching or perform some actions when a user opens the email.
– API limitations. OWA add-ins are limited with the API provided by the Microsoft so some things are not possible to do out of the box. For example, there is no way to handle events like Email Sent or others that can be critical for some type of add-ins.
How to build your custom OWA add-ins
There is a great add-in code example created by Microsoft on their website. The following are some links for the smooth start of OWA add-in development:
– Get Started with Outlook add-ins for Outlook.com
– Demo add-in that shows you how to work with Task Pane, Ribbon commands, Mail items