When you send email using Evolution Mail, you may find that all of your emails say "Sent from Ubuntu" at the bottom of them. This is the default email signature that was introduced with Ubuntu 10.10 (Maverick Meerkat), and it is easy to change or turn off.
Open Evolution Mail (Applications -> Internet -> Evolution Mail).
Click Edit -> Preferences and select Mail Accounts.
Select your email account and click Edit.
Under the Identity tab, look for the Optional Information section. Change the Signature option to something else, like None.
If you don't want to use any of the existing options, click Add New Signature to add your own custom signature.
Click OK and close the Preferences window. The next time you write a new email, the signature at the bottom will have changed.