Here's How to Automatically BCC an Address in Mac Mail

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macOS Mail keeps a copy of every message you send in the Sent folder, but there's another way to keep a more permanent and regular version of each message. You can do this by automatically emailing a copy of each email to your own archive email address.

To do this requires that you add that archive address to the Bcc field for each message you send out. Of course, you could do this manually but it's much easier to let macOS do it for you.

Another purpose for setting up an auto-Bcc email, apart from creating your own auto-archive, is so that you can automatically email someone else each time you send out new mail, which is great if you already find yourself doing this manually.

How to Auto-Bcc Every New Email

Here's how to add a specific email address to the Bcc field of every new email you send out from Mac Mail:

  1. Type defaults read UserHeaders.

  2. Press Enter.

  3. If the command returns a message that reads "The domain/default pair of (, UserHeaders) does not exist," then type:

    defaults write UserHeaders '{"Bcc" = "bcc@address"; }'

    Make sure to replace bcc@address with the email address you want to be used for the automatic blind carbon copy.

    If the "defaults read" command above returns a line of values that starts and ends with brackets like { and }, then continue on with Step 5.

  4. Highlight and copy (Command+C) the entire line. It might read something like:

    {Reply-To = "reply-to@address"; }
  5. Type the following command in Terminal:

    defaults write UserHeaders '
  6. Now paste (Command+V) what you copied in Step 5 so that the entire line reads something like this:

    defaults write UserHeaders '{Reply-To = "reply-to@address"; }
  7. Close the command with an ending quotation mark and then insert "Bcc" = "bcc@address"; before the closing bracket, like this:

    defaults write UserHeaders '{Reply-To = "reply-to@address"; "Bcc" = "bcc@address";}'
  8. Press Enter to submit the command.

Unfortunately, this neat trick has a major drawback in that macOS Mail will replace Bcc: recipients you've added while composing it with your default Bcc: address. If you want to add a different Bcc: recipient than the one you've chosen to add automatically, you either have to set it via Terminal like described above (separate multiple addresses with a comma) or remove Bcc from your UserHeaders before sending the email (make sure you quit Mail before making any change).

How to Disable Automatic Bcc

Use this command in the Terminal to delete the custom headers and turn off automatic Bcc emails:

defaults delete UserHeaders

The other option is to set UserHeaders back to what it was before you added Bcc.