mp4 file won't launch from email

[Peter Creasey]

I have VLC installed on my W10 Home PC.

Launching an mp4 file received as an email attachment in SeaMonkey email processor gets the error message "Video format or MIME is not supported". It launches fine from the web mail copy of the email

Is this a FireFox/ThunderBird/SeaMonkey shortcoming or can this be remedied?

Thanks.

[Anonymosity]

Can you not detach the attachment and then play it from the download directory?

[Peter Creasey]

Yes, I can work around the problem a couple of ways; however, I was hoping to learn the solution that will allow me to just double click on the attachment in the SM email message.

I'm a very longtime user/admirer of SM so it pains me that a problem like this can be a detraction.

[hardys]

What happens when you drop a mp4 file in the browser?
With SM 2.53 the videos play without errors also when opening from mail.
When you visit this site https://www.youtube.com/html5 are all files supported?

[Peter Creasey]

The mp4 file runs fine when launched from web mail.

I don't know how to answer your last question.

[hardys]

Does it look like this when you visit the site https://www.youtube.com/html5:



Then all video formats are supported and mp4 files will play in the browser as HTMLVideoElement.

[Peter Creasey]

Yes, except "MSE & WebM VP9" has a red exclamation mark in a block beside it.

[hardys]

Do you want the mp4 to be opened in Seamonkey or VLC?
Normally mp4 will be played in SM. When you disable mp4 support in SM prefs (not recommended) then you will be asked if you want to save the file or you can choose e.g VLC to play the file.

[Peter Creasey]

I don't whether I should prefer one or the other. If it's not _risky_, I would prefer to be able to click on the file from SeaMonkey email and have it launched.

[Peter Creasey]

Interesting update. I received an mp4 file and it readily launched from SM email.

Go figure!