"We can't open '....' - It's possible the file is already open, or you don't have permission to open it." when trying to access an email

Issue
I am trying to export an email to access attachments. I also cannot open, forward, or reply to this email. I get the following error:

"We can't open '....' - It's possible the file is already open, or you don't have permission to open it. To check your permissions, right-click the file folder, then click Properties"

Cause
You have imported an email in .msg file format.

Due to the restrictions of Microsoft, we do not support emails imported in the .msg file format. You can therefore not open, export, or forward an email.

Workaround

1. Convert the .msg file to an .eml file using the following free website converter Zamzar:
   https://www.zamzar.com/convert/msg-to-eml/
2. Import the .eml file to FYI using Drag and Drop or via your FYI - My Imports OneDrive folder (refer to Drag and Drop and Using OneDrive FYI - My Imports to Automatically Import to your In Tray).