Change Mail settings
Use Mail Preferences to set or change options for the email accounts you use in Mail, and for working with messages and mailboxes. Choose Mail > Preferences, then click a preference pane to view options:
General: Change settings that range from how often to get messages, to the kinds of messages to include when searching for messages in Mail.
Accounts: Add, delete, and disable your email accounts in Mail. Use the Mailbox Behaviors pane to control how draft, sent, junk, and deleted (or “trash”) messages are stored. The Advanced pane includes options for messages, attachments, and more.
Junk Mail: Enable the junk mail filter and change settings to improve it.
Fonts & Colors: Select the fonts and font sizes used to display messages.
Viewing: Change settings to control how messages are shown in the Mail window.
Composing: Change settings for spell checking, and for addressing and replaying to messages.
Signatures: Create signatures and have them automatically appended to all of your messages, or use them in only some messages.
Rules: Create rules to do things like have messages from a certain person automatically moved to a mailbox, or highlight messages about a birthday party.
To learn about the options in a pane, click the Help button at the bottom of the pane.