[Enigmail] gpg signatures and html

[Faramir]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
 
Hello!
~         I have been using enigmail in Thunderbird (windows version) 
for a while, and, after reading the quick start guide, I know I must use 
plain text to avoid breaking my signature. However, I have recived 
emails with emoticons (those funny faces), and the signatures in these 
emails were valid... so, I suppose there is a way to sign emails made in 
html, instead of plain text... but I dont have any idea how to do 
that... any hint you can give me?

~        Thanks
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
 
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Vov1GoY5E8oWZXtcOB/bfVssro9IsFMnl3HsI0EovYZv3TKdcWQuC7hfPQMX5AY=
=2QEf
-----END PGP SIGNATURE-----