Change Composing preferences in Mail on Mac
Use Composing preferences in Mail to change options for messages that you create.
To change these preferences in the Mail app on your Mac, choose Mail > Preferences, then click Composing.
Use plain text or rich text (HTML) to format your messages.
If a recipient’s email app can’t view rich text, a plain version of the message is displayed.
Check spelling automatically as you type a message, when you click Send, or not at all.
Automatically [Cc or Bcc] myself
Automatically receive a copy of every message you send.
When sending to a group, show all member addresses
Show each email address in the group, instead of just the group name.
Mark addresses not ending with
Show email addresses that don’t end in a specified domain in red, to help prevent you from sending messages to unintended recipients.
Send new messages from
The email address to use when you send messages.
If you use several email accounts, you can have Mail automatically select the best address, based on the email address of the first recipient in your message, as well as the currently selected mailbox and message.
Use the same message format as the original message
When you reply to or forward a message, use the same format as the original message.
Quote the text of the original message
When you reply to or forward a message, include the text of the original message as quoted text.
Increase quote level
When you reply to or forward a message, indent any text you include from the original message.
When quoting text in replies or forwards
When you reply to or forward a message, include all the text or just selected text from the original message.