For composing mails I've actually got it set to plain text, so I've never seen this issue until I started using XF's contact form to receive mails. I don't recall this spacing issue happening with other e-mails containing HTML, anyway. It seems that this only happens when responding to e-mails where a contact form HTML version is the first message in the correspondence. I'd rather not force convert everything to plain text if the issue is limited to XF only but rather just change the outgoing contact form mail to be plain text only... I've seen the plain text/HTML toggle in other places so I was surprised that it's not available for the contact form. Would just copying the plain text template and pasting it into the html one cause any problems?