Office.context.mailbox.item.addFileAttachmentAsync() fails in Outlook Web on-prem (Exchange Server 2019 v15.2, build 1544.4)

[GruberMarkus]

Provide required information needed to triage your issue

Your Environment

• Platform [PC desktop, Mac, iOS, Office on the web]: Office on the web (on premises)
• Host [Excel, Word, PowerPoint, etc.]: Outlook
• Office version number: Outlok Web on Exchange Server 2019 (version 15.2, build 1544.4)
• Operating System: Multiple (Windows 11 latest, Ubuntu 22.04, macOs Sonoma latest)
• Browser (if using Office on the web): Edge (latest version), Firefox (latest version)

Expected behavior

Office.context.mailbox.item.addFileAttachmentAsync() should add an attachment.

Current behavior

When calling Office.context.mailbox.item.addFileAttachmentAsync(), the folloing error is returned: {"name":"Host Error","message":"The operation is not supported.","code":5000}

Steps to reproduce

1. Create a taskpane add-in for Outlook
2. Add a file using Office.context.mailbox.item.addFileAttachmentAsync(<public URL to image file>, "my file name.jpg", { isInline: false})
3. Deploy add-in
4. Run in Outlook Web on premises

Link to live example(s)

Not available

Provide additional details

The very same code works fine in Outlook Web running on Exchange Online, as well as in Classic Outlook on Windows. Other platforms have not been tested.

Please let me know how to avoid this error. addFileAttachementFromBase64Asynch() is not an option, as it is not support in Outlook Web on premises.

Edit: Replace Office.context.mailbox.item.addFileAttachmentFromBase64Async() with Office.context.mailbox.item.addFileAttachmentAsync() in sample code and error description.

[Oleg-O]

This API was added in requirement set 1.8; but per the support table on this page, Outlook Web on-premises supports up to and including 1.6 only, so this is expected.

[GruberMarkus]

According to the documentation of the method at https://learn.microsoft.com/en-us/javascript/api/outlook/office.messagecompose?view=outlook-js-preview&preserve-view=true#outlook-office-messagecompose-addfileattachmentasync-member(1), the required API is 1.1.

From what I see in the API 1.8 release notes, addFileAttachmentFromBase64Async has been introduced with 1.8, but not addFileAttachmentAsync (without Base64).

I mixed up these two myself in the bug description. Sorry for that.

The problem is with Office.context.mailbox.item.addFileAttachmentAsync().

Could you please have another look at this topic?

Edit: I replaced Office.context.mailbox.item.addFileAttachmentFromBase64Async() with Office.context.mailbox.item.addFileAttachmentAsync() in sample code and error description of the opening comment.

[Swathy-Mothilal]

Hi @GruberMarkus, Could you please let me know if this was functioning as expected previously and since when are you experiencing the issue?

[GruberMarkus]

No, I can't. I am only using Office.context.mailbox.item.addFileAttachmentAsync() since a few days.

[Swathy-Mothilal]

@GruberMarkus Thanks for the confirmation. We are able to repro the bug, and have put it in our backlog. Unfortunately, we don't have any timelines to share.

Internal tracking id: 4944585