Software Development Insights

GBS Outlook Add-in

Outlook add-ins are integrations developed by third parties in order to extend Microsoft Office Outlook functionality beyond the core set. They enable users to share different content (such as tasks, experiences etc.) without leaving their inbox. By essence, add-ins are HTML, CSS, and JavaScript files hosted on the web server. Being installed, they are available on any platform and device.

GBS Outlook add-in is a custom solution developed by the Gunnebo Business Solutions team in partnership with Diceus.

The main purpose of the GBS add-in is to synchronize Outlook Tasks and Schedule between the users of Outlook profile and the GBS platform. It allows users to optimize time for workflows and ensures optimal comfortable distribution of tasks and events.

Key Features

Compared to Windows add-ins (such as COM and VSTO), Outlook add-ins don’t contain any pieces of code which should be added to the Outlook client. In contrast, all the processes are carried out in a browser sandbox. Outlook actually only reads the manifest and hooks up HTML and JavaScript-generated controls in the UI from the Azure storage.

Gunnebo Outlook Add-in is supported by all versions of Outlook starting from 2013, Outlook 2016 for Mac, Outlook Web App for Office 365 and the service.

Technical Implementation

For the GBS add-in, we implementer schedule synchronization in the calendar, and tasks in the task manager of the GBS platoform. We originally planned to use JavaScript, but it doesn’t allow background synchronization as scripts are run only when the browser is active, thus, the process stops when the user closes the tab. To get around this issue, we added a scheduled background Rest API microservice based on .NET core:


Then we improved sync by adding fault tolerance: sync process uses hashes instead of IDs, and each hash could be rewritten and continued. Even if something goes wrong in the middle of the sync, we can return and restart the whole process – nothing will break.

The algorithmic complexity of syncronization is O(n), because we go linearly through two lists, one in Outlook and one in GBS.


There can be several solutions to this challenge. The more advanced one is not to use current status of tasks and events. We can track only their changes, as with version control. This works for events and tasks changes, but since we don’t have them, we use hashes instead of version history control.

Using the GBS Plugin

Install the GBS add-in the Outlook client, then sign in with your GBS account and Microsoft Outlook account:

Thanks to the GBS Outlook add-in, the end user can significantly optimize their workflow and business processes without complex settings and installing any additional programs. They can even enjoy creation of custom work schedules and easy and quick access the information from their e-mail client or within the GBS platform.

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