HTML Signatures - not sending correctly

Hi, i have moved across to Manjaro - KDE from Windows on my main PC,
we have Email signatures written in html that i was using in Outlook.

when i setup the signatures in Kmail, the table border is not visible on my end, but when i send it, it seems to loose all formatting for the table.

I copied the code for the signature into thunderbird, it it appears fine,

it seems like it sends emails in rich text format instead of HTML possibly?
am i missing something?

Just boosting this thread hoping someone has an answer as I’m having the same issue. The image links don’t work either for mine.