This topic answers your questions about how to modify the settings for your mail.
How Do I Set the General Preferences in Mail?
How Do I Set a Signature for the Messages I Compose?
How Do I Set the Layout of the Messages in my Inbox?
How Do I Enable Automatic Forwarding of Messages?
Mail Filters
How Do I Set a Vacation Message?
Sender Identities
Collecting Email From External Accounts
Security