There are a number of ways to customize your r mail experience in the application settings.
The Default action icon is discussed here.
Unchecking Show Emails in Folders hides emails you have sorted into folders from the main email list.
Delete emails without prompt disables the confirmation popup window from appearing when you try to delete an email.
You can set up multiple Email signatures for each of your r-evolution email accounts. To set a signature, click on the Email Signatures setting and press the icon to create a new signature. Select the account you would like to associate the signature with, name the signature, and enter the signature itself in the main field.
Your new signature will appear in the signature list along with any others you have created.
Back in r mail, you will notice a new icon on the create email screen. Press the icon to add a signature to your email.