How-to edit X-Mailer header of Apple Mail?

[MacFrag]

Does anybody know how to edit the X-Mailer header on all emails when you send mail?

I want to hide which email program I use.

Now (by default), on every email I send with the Mail program it inserts:

X-Mailer: Apple Mail (2.3445.6.18)

In Thunderbird this is done very easily by creating an empty value of general.useragent.override, but I want to use Apple mail also.

 

[chown33]

See here:
https://www.lifewire.com/add-reply-to-header-os-x-mail-1172899

Found by googling: apple mail send header


Simplified summary:

defaults write com.apple.mail UserHeaders '{"X-Mailer" = "incognito"; }'

To revert:

defaults delete com.apple.mail UserHeaders

 

[MacFrag]

Thank you chown33!

I Googled before but did not used the right *key words* apparently (blush).

After setting X-Mailer it still leaks your Mail client info by the Mime-Version header.

To fix that also you can add Mime-Version also to UserHeaders.

Used "Outlook" for example purposes only.

defaults write com.apple.mail UserHeaders '{"X-Mailer" = "Outlook";"Mime-Version" = Outlook; }'

 

[bsmr]

This doesn't work for me with Version 12.4 (3445.104.11)

Also tried:
defaults write com.apple.mail UserHeaders '{"X-Mailer" = "";"Mime-Version" = 1.0;}'

But still showing the version and the client within the header

 

[chown33]

Try using the exact example given in post #3. That is, use "Outlook" for both values.

Reboot after changing it. The setting might not take effect immediately.

Copy and paste this command into Terminal:

defaults read com.apple.mail UserHeaders

Then copy and paste the entire exact output into a post here, to confirm it was set.

If nothing works, then it's possible Apple removed the setting. This has happened before with other apps.