Setting mutt on FC7

[hce <webmail.hce@xxxxxxxxx>]

Hi,

I've just set up the mutt on FC7 using vim editor. Appreciate any
helps for my following questions:

1. The receiving mail seems ok, but I could not post mails. On the
menu, there is a o:Mail, but when I pressed the o key, it always print
out "Aborted unmodified message.", it did not bring me to the edit
page, the same when I pressed "r" key for replying. How can I fix it?

2. I'd like to set up color in white when I reading the mail, but
there are two lines, "Subject:" and "From:" are always in red. How can
I set up the color in muttrc to make those two lines to white?

3. How can I setting a signature to attach a jpeg file or doc file? Is
it like following set in the muttrc?
set signature="~/mysignature.doc"

Thank you.

Kind Regards,

Jim