[support] Mimemail sending CSS

[Bob Morse]

Using MimeMail (6.x-1.x-dev) with Simplenews (version 6.x-1.0-rc6), with 
html turned on, some people get the message with a ton of css code in 
it. It's odd because we tested this and didn't see any code. But we 
received several messages from people who received code in the body of 
the message. Some spam filters blocked the message because of all the 
code. I posted on MimeMail issues but with no response yet.