mozilla thunderbird - icedove hide user agent

To hide (obfuscate or not send) the User agent header in thunderbird and icedove

open the config editor and look for general.useragent.override

If it does not exist add it ( type: string )

You may set it to a value --string or leave it empty.

If you leave it empty Thunderbird/Icedove will not add a User agent Header to your outgoing emails.