I have an SR open on this, but also wanted to share the issue here and follow up with resolution.
I am finding that appointment requests that come in with attachments that are threat extracted are delivered as email messages rather than appointment requests.
If an external user sends an appointment request with an attachment, and the attachment gets threat extracted, instead of getting an appointment request, I get an email with the threat extracted attachment, but none of the appointment information.
If I restore the attachment, then the appointment request message pops into the inbox. I was able to replicate this successfully using an Excel spreadsheet.
The sender and recipient accounts are both Office365, and the email clients are Office 2016 or whatever the latest is.
Anyone else run into this?