Also, there doesn’t seem to be a distinction of client’s versions… shouldn’t there be one?
The client versions are displayed on each element’s advanced section, for example:
! !
And also I don’t see Thunderbird email client in the list of desktop apps… it’s not identified at all (it’s in “other” category) or it’s just hidden somewhere?
According to https://help.mailtrap.io/article/60-html-check#filtering, Thunderbird is listed as “less popular client” and listed on “Other” category.
Also, what is the Gmail in the list of desktop clients? Is there such a thing?
Actually I’m not really sure what they mean by that (I’ve also searched a little bit in their documentation), as there isn’t an official Gmail Desktop app, but apparently there is an workaround for it: How to get Gmail as a desktop app.