You go to "hamburger" and select Settings. Then go to General, then at very bottom at far right, click button "Config Editor" In config editor search bar, enter ```customh``` and you should see mailnews.customHeaders Click the "pen" icon to edit or remove the custom headers. FWIW, when I edit to this ```x-send-later-at: x-send-later-recur: x-send-later-args: x-send-later-cancel-on-reply: x-send-later-uuid: content-type: x-support-newsletterATflightaware-com``` it works. Then to save click the check mark. Best to restart to make sure TB sees the change.
Bug 1846109 Comment 20 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
You go to "hamburger" and select Settings. Then go to General, then at very bottom at far right, click button "Config Editor" In config editor search bar, enter ```customh``` and you should see mailnews.customHeaders Click the "pen" icon to edit or remove the custom headers. FWIW, when I edit to this ```x-send-later-at: x-send-later-recur: x-send-later-args: x-send-later-cancel-on-reply: x-send-later-uuid: content-type: x-support-newsletterATflightaware-com``` it works. Then to save click the check mark. Best to restart to make sure TB sees the change. Edit: I've never used or help anyone with custom headers. But this describes what they do: https://kb.mozillazine.org/Custom_headers
You go to "hamburger" and select Settings. Then go to General, then at very bottom at far right, click button "Config Editor" In config editor search bar, enter ```customh``` and you should see mailnews.customHeaders Click the "pen" icon to edit or remove the custom headers. FWIW, when I edit to this ```x-send-later-at: x-send-later-recur: x-send-later-args: x-send-later-cancel-on-reply: x-send-later-uuid: content-type: x-support-newsletterATflightaware-com``` it works. Then to save click the check mark. Best to restart to make sure TB sees the change. Edit: I've never used or helped anyone with custom headers. But this describes what they do: https://kb.mozillazine.org/Custom_headers
You go to "hamburger" and select Settings. Then go to General, then at very bottom at far right, click button "Config Editor" In config editor search bar, enter ```customh``` and you should see mailnews.customHeaders Click the "pen" icon to edit or remove the custom headers. FWIW, when I edit to this ```x-send-later-at: x-send-later-recur: x-send-later-args: x-send-later-cancel-on-reply: x-send-later-uuid: content-type: x-support-newsletterATflightaware-com``` it works. Then to save click the check mark. Best to restart to make sure TB sees the change. Edit: I've never used or helped anyone with custom headers. But this describes what they do: https://kb.mozillazine.org/Custom_headers Note also, the ```content-type``` header is a default header TB always asks for. So not really needed in the customHeaders list.