Outlook 加载项 - 附件 ID 在桌面应用程序中无法正常工作，但在 Web 应用程序中可以正常工作

Question

I've developed an add-in for Outlook, it needs to be able to access attachments to emails.

On the desktop app, if I move an email with attachments from a shared folder to my main inbox, then try to run the add-in on it, i get the error:

The specified attachment Id is invalid.

However, if I perform exactly the same operation through the web app, it works fine.

I have checked and the Office.context.mailbox.item.itemId and Office.context.mailbox.item.attachments[i].id are exactly the same whether on web or desktop.

Emails with attachments that have not been moved from a different folder, and emails without attachments work fine.

I am fetching the attachment on a remote server through a PHP script, using a callback token I orginally get from Office.context.mailbox.getCallbackTokenAsync . The requests are made via EWS requests.

I am running Office 365 and the Outlook version is 1910 (Build 12130.20390), running on Windows 10.

Can somebody please help?

Answer 1

After some helpful suggestions from @OutlookAdd-insTeam-MSFT, I've come to a solution for this.

The problem is, after moving a message from a shared folder to the main inbox, when using the desktop app, the Office.context.mailbox.item.attachments (created when we run Office.initialize ) no longer returns the correct ID's, instead it seems to return the old cached/out of date ID's from before the email was moved. The ID's returned when using the web app are correct using this method.

However, requesting the ID's from the exchange server, via an EWS request (or a REST call, but I use EWS) always returns the correct attachment ID's, whether called from the web app or the desktop app.

So, the solution I have come to is to make sure and request all of the attachment ID's from the exchange server, rather than using the Office.context.mailbox.item object. It means adding in an extra step of having to get a callback token first to then be able to request the info from the exchange server, but it means you always get the correct ID's.

I hope this is of help to someone else.