Change Signatures preferences in Mail on Mac
Use Signatures preferences in Mail to create signatures you can add to messages you send.
To change these preferences in the Mail app on your Mac, choose Mail > Preferences, then click Signatures.
Choose signatures to work with by clicking All Signatures or an email account.
The list of signatures in All Signatures or an account.
When All Signatures is selected, you can add an existing signature to another account by dragging the signature from the middle column to the account in the left column. You can use the same signature in more than one account.
Add , Remove
Create a new signature for the selected account or remove a signature.
If you create a signature while All Signatures is selected in the left column, you must drag the signature to an account before you can use it.
Type the text of your signature, and preview how your signature will look.
Use the Edit and Format menus in Mail to change the font or layout, turn text into links, or check spelling. To add an image, drag it into the column. To quickly include your contact information, drag your card from the Contacts app into the column.
Always match my default message font
The selected signature uses the message font specified in Fonts & Colours preferences.
Select a default signature to automatically include in your messages for the selected account, or instead use all of the account’s signatures in sequential or random order.
Place signature above quoted text
Position your signature when you reply to or forward a message.
If you use iCloud Drive, your signatures are available on your other Mac computers that have iCloud Drive turned on and Mail selected in iCloud Drive options. See Use iCloud Drive to store documents.