To receive a blocked message from a sender, have the sender rename the file to an extension that is allowed (recommend renaming to .jmu) and resend.
Once the file arrives, save it and rename it to the original extension.
Note: To see the file extension in:
Windows 10:
- Click the Windows icon
- Type the words "file extension" and click on the option Show or Hide File Extensions to turn it on
- Click OK
MacOS 10.14 and later
- Click on the desktop to activate Finder
- Click Finder at the top and Select Settings
- Click the Advanced icon (looks like two gears)
- Check the Show all file extensions box. All file extensions will now be visible both on the desktop and in open windows.