Could you copy-and-paste some of this "stupid computer notation" or else provide a screenshot?

Here is an example - the e-mail I received from Mozilla telling me that you had posted in reply to my query. (It reads fine on my iPad but looks like this in Thunderbird on my PC)

Screenshot attached as thunderbird.jpg

View (Alt-V) - Headers - Normal

Headers are already normal but I still get the gobblygook.

Normally, the stuff you have reported shows up in the message header panel above the message text. In such cases the View|Headers switch suggested to you would swap between showing all of this ("All") and just the most important bits ("Normal").

But it looks to me as if your message body is actually showing the so-called message source.

And I don't know what would cause that, other than malformed messages where Thunderbird couldn't correctly identify and separate the header text and the message text.

Could I ask you to forward an example of one of these messages via email as an attachment please?

xenos at gmx dot co dot uk