What is the benefit of signing an encrypted email

[Olav Seyfarth]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: RIPEMD160

Hi Jim / Bob,

> In Firefox I can sign or encrypt or encrypt+sign an e-mail.
> In what case would I want my encrypted emails also signed?
> Does it provide any additional benefit over a pure encrypted email?

encrypted = only persons you encrypted TO can read your message
  (= these persons need to have set up a key themselves beforehand)

signed = everybody that has access to your PUBLIC key can verify
  that your message has not been fiddled with since you signed it

Olav
- -- 
The Enigmail Project - OpenPGP Email Security For Mozilla Applications
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.16 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
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=scf0
-----END PGP SIGNATURE-----