Office Add-ins community call -- July 2021

Call summary

This month’s community call features presentations - Shared mailboxes in Outlook (Shared Mailbox vs Delegate Access/Shared Folder, Shared Mailbox design considerations and add-ins) and PnP: Message recipients changed event (Outlook) (If external recipients are detected in an e-mail’s list of recipients, than the message is automatically tagged as External and optionally a disclaimer is appended to message).  This month’s Community spotlight recognizes James Wayne (Exclaimer) for his continued contributions.  Thank you!   Q&A in chat throughout call.  The call was hosted by David Chesnut (Microsoft) | @davidchesnut. Microsoft Presenters: Juan Balmori | @juaneloBalmori, Ankush Oberoi, and Elizabeth Samuel.   Recorded July 14, 2021.


  • Shared mailboxes in Outlook – Juan Balmori (Microsoft) | @juaneloBalmori – 00:50
  • PnP: Message recipients changed event (Outlook) - Elizabeth Samuel, Sr. Dev Writer (Microsoft) – 11:13
  • Shared mailboxes Demo - Ankush Oberoi (Microsoft) – 22:37
  • Q&A – 26:45

Demo Summaries

This month’s community call featured presentations:

  • Shared mailboxes in Outlook - Juan Balmori (Microsoft) and Ankush Oberoi (Microsoft) discussed shared mailboxes and shared folders. Shared mailbox is now in preview and we encourage you to try it out and give us feedback at
  • Message recipients changed event for Outlook - Elizabeth Samuel (Microsoft) shared a new PnP sample demonstrating how to use the Recipients Changed event to tag an email when there are external recipients.

Q&A (Question & Answers)

Due to the technical difficulties we had on this call, we could not access the chat to read your questions and provide follow-up. If you had a question that did not get answered during the call, or in this blog, please reach out to us by using our short survey form. We’ll address any questions you have during the next call.

Can you add some additional error handling around failure cases for an Outlook add-in that uses the On-send event? We have a scenario where if an On-send add-in fails due to service outage users are unable to send emails unless an admin performs a companywide deactivation of the add-in. It would be helpful to let end-users still send their emails if the On-send add-in fails to load or throws an unhandled exception.

That’s by design for the On-send event when we released the 1.8 requirement set. The good news is that the team is working on enabling a new version of this event that will deal with the “add-in unavailable” cases. We are working to get this into preview soon, so please keep an eye out on future community calls.

On the iOS and Android platforms, you only support Outlook API 1.5. Do you think we will see support for 1.6+ before 2022?

We have this in our backlog, but we don’t yet have an ETA.

Outlook on mobile still does not support compose mode add-ins, or the On-send event. This was a highly requested feature on the UserVoice system. When will Outlook on mobile support both of these? How did the ‘Exclaimer’ add-in from June 2021’s community call work on Outlook mobile without support for compose mode add-ins?

We have this in our backlog, but we don’t yet have an ETA. The Exclaimer add-in isn’t designed for use on Outlook on mobile.

Is there a way to write a CSV file to the local computer’s storage where the add-in is running?

Office Add-ins run in a browser runtime and only have the capabilities of any web app running in a browser. It’s not possible to write directly to disk from the browser in any way that works cross-platform. A recommended approach to write to a CSV file is to write to files using Microsoft Graph and OneDrive.


Outlook shared mailbox

PnP: Use Outlook event-based activation to tag external recipients (preview)

Office Add-ins community call

Office Add-ins feedback

The next Office Add-ins community call is on Wednesday, August 11, 2021 at 8:00AM PDT. Get the calendar invite at