There are three pages for settings you can change for the message composer. The General page covers shortcuts and assorted behavior, the Signature page controls your signature, and the Spell Checking page controls spell checking.
In the General page, you can set the following options:
Default Behavior: Choose how you will normally forward and reply to messages, what character set they will use, whether they will be in HTML, and whether that HTML can contain graphic emoticons.
Alerts: There are two optional alerts you can select:
Prompt When Sending Messages With an Empty Subject Line: The composer warns you if you try to send a message without a subject.
Prompt When Sending Messages with Only Bcc Recipients Defined: The composer warns you if you try to send a message that has only Bcc recipients. This is important because some mail servers fail to transmit blind carbon copy if you do not have at least one recipient that is visible to all readers.
The signature editor allows you to create several different signatures in plain text or in HTML, and to specify which of them will be added to e-mail you create in the message composer. If you prefer to use an alternate signature or none at all, you can select it from the mail composer itself.
To choose a spell-checking language, select it here. You must install the gnome-spell package, available through ZENworks® Linux Management, for spell-checking to be available in Evolution. Additional dictionaries are also available through Red Carpet® and are detected automatically if you have installed them. To have the composer automatically check your spelling while you type, select Check Spelling While I Type.
Check the spelling in messages by clicking Edit > Spell Check Document.