Can't View Thunderbird Emails in UR

[J-Mac]

I can no l9onger view emails from Thunderbird in URp. I was able to do this before using the MIME reader but that isn't working now. The Manual says to instead use the Forms Control and have the .eml and .nws extensions listed in the appropriate box in Editor or Browser. I have tried the Editor options, Browser options, and I even went back to the MIME viewer - nothing allows me to view my Thunderbird messages in URp. As soon as I click on an email message UR opens it in an external Thunderbird viewer.

What happened? Has this feature been removed? Are the settings different now?

How can I view email messages within URp?

Thank you.

Jim