text format question

[Tony Alfrey]

Possibly a dumb question and possibly not a linux questions :-(
I use Thunderbird (on my Mac) and when I look at the message source I see

Content-Type: text/plain;
               charset=ISO-8859-1;
               format=flowed

Does anyone know how I can make it

Content-Type: text/plain;
	charset="US-ASCII"

I have a list of character sets to choose from, but I do not see US-ASCII.

Thanks!


-- 
Tony Alfrey
tonyalfrey at earthlink.net
"I'd Rather Be Sailing"