I just sent an email to myself with an animated gif and it worked fine. And the animation was viewable in message window. You may have some setting or addon that prevents it.

Thanks for the quick reply David! I testing Thunderbird 91.6.0 64-bit on my test Windows 7 Pro. It is a base install with no add-ons I did. If I put an animated gif in the body of an email, it doesn't "move" until it is in the "sent" folder. What about sound? I've attached a sample that WLM handles for you to try in your TBird. I've set up the html file "laughing Gopher.htm" as a signature in WLM and when I add it to an email, it moves and laughs. I'm testing other email programs as WLM has started to crash occasionally. Thanks... Well, I can't attach it, so hopefully you can download it using... https://drive.google.com/file/d/1B52zDkUdYAjUONDryqBuXk9eU5spzrWD/view?usp=sharing

I received your gopher and it works fine in sending and receiving. TB doesn't autoplay sounds (which I think is good), but lets user specify an app to play on request.

Thanks David... I'll play around with settings and see if I can get it to work.

If I put an animated gif in the body of an email, it doesn't "move" until it is in the "sent" folder.

That sounds correct. In the same way a link is not activated as a link until it is saved and viewed as a draft or sent and viewed in sent folder.

To test added gif - save as draft, then access 'Drafts' folder and select the newly saved draft. You should see it activated.

All working ok in my version 91.6.0