I'm interested in doing this to add an "Approved:" header to a Mailman announcements-only list (reference).

2 Answers 2


If you are using the Gmail web interface the answer is no, it's not an available option. However, you can bypass this restriction by sending an email using a script or any other tool where you can control the headers and using the Gmail SMTP to deliver the message.

Every programming language allows you to write a script to deliver an email. There's also a ton of pre-packaged scripts you can download, install and customize. Make sure to use Gmail SMTP so that the email will be stored in your Gmail account.


You can use Thunderbird to edit and send email messages from your Gmail account.

Here's an extension called Header Tools Lite that helps you modify the header info in your email message.

  • So is there a Chrome extension that does it?
    – Pacerier
    Nov 23, 2017 at 19:15
  • 1
    @Pacerier, not that I'm aware of, and based on my understanding, I would suspect it's not possible at that point in the pipeline. Emails cannot be sent from a browser / client. How any email web app works is by passing a HTTP(S) message to their own servers and then based on their own internal APIs / method, sending the email from their domain. Unless they were to expose header info as a parameter, there is no way to get that info to them via an extension. What Thunderbird is doing is driving the email generation from scratch, so you can do anything you'd like before sending.
    – KyleMit
    Nov 24, 2017 at 18:09
  • I use Thunderbird on Windows and added custom headers without an extension, like this person: webapps.stackexchange.com/a/11810/27487
    – Ryan
    Dec 11, 2019 at 21:53

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