Select only email addresses in the List-Unsubscribe header

[Tanaka-tnk]

Expected Behavior

I would like to configure the List-Unsubscribe header to include only email addresses.

Current Behavior

The List-Unsubscribe header contains two parts: the URL and the email address.

Context

I want to use the web interface to set up my mailing list, but I don't want my list readers to have access to the web.I have tried adding only email addresses to the List-Unsubscript header with the “custom_header” option, but that failed.