Save and Use Messages as Templates in Mac OS Mail

To save a message as a template in macOS Mail:

1. Open Mail.app > Mailbox (in menu bar) > New Mailbox.
2. Select for the mailbox and type "Templates" into the name field.
3. Create a new message.
4. Edit the message to contain anything you want in the the template.
   o You can edit and save the message subject, contents, recipients and/or the message priority.
5. Select, File > Save as Draft from the menu.
6. Close the message editing window.
7. Go to the Drafts folder.
8. Move the message you just saved from the "Drafts" folder by dragging it to the "Templates" folder.

To use a message template in macOS Mail to create a new message:

1. Open the "Templates" folder containing the desired message template.
2. Highlight the template you want to use for the new message.
3. Select Message > Send Again from the menu.
4. Edit and send the message.

You can also use any message you previously sent as a template by copying it to your "Templates" folder (or using Message > Send Again directly). To edit a template, create a new message using it, make the desired changes and the save the edited message as a template as described above while deleting the old template.