I just noticed that the font size does not pass either when using "size" on the toolbar but it does when you use "format" and change to a "header" style. here is the code from the source email.
This did NOT change the font in the email:
--b1_d2203fd13f042e3a0d5e6ff255184de2
Content-Type: text/html; charset = "iso-8859-1"
Content-Transfer-Encoding: 8bit
<p>
<span style=\"font-size:28px;\"><span style=\"background-color:#ffff00;\">test message </span></span></p>
--b1_d2203fd13f042e3a0d5e6ff255184de2--
This worked like it should, because I used "Header 1"
--b1_558445700dbf30c67970dad32ef42eb6
Content-Type: text/html; charset = "iso-8859-1"
Content-Transfer-Encoding: 8bit
<h1>
test message</h1>
--b1_558445700dbf30c67970dad32ef42eb6--