I regret you are not getting the feedback you want, but it's difficult to assess the issue. Does the email work when using plain text? Have you tried installing Thunderbird directly on top of current installation, just in case something was corrupted? Is every email messed up, or just a few?

Actually, it seems to be only a problem with win 10 for workstations (my other installs (wife, work) are just fine!. plain text mostly works, but why should it show the coding? T/bird was reinstalled twice...no difference... As an example, your e-mail was OK (view as original html), but that was the same setting as the corrupted image I sent. Some are OK, some corrupted. ??? I can change to view as simple html, but embedded images are (of course) lost...I often use the images for electronics diagrams (png, tiff)...

Any ideas why win10 for workstations should be affected? Tom

Hello

well, 4 processors for a windows end user computer - does not sound a common configuration, it could emerge some unusual behaviour. Maybe some obscure bug in Firefox kernel rendering ? could you check this by using task manager and setting affinity for Thunderbird to use only one processor ? I could link to some tutorial on the web but unfortunately posting links on this forum leads to bizarre delays for posts to appear.

Also, if your mails are not too confidential, maybe you could post the headers from a mail that is coming badly and one appearing correctly.