Thunderbird:Help Documentation:Mail-Followup-To and Mail-Reply-To

Mail-Followup-To (MFT) and Mail-Reply-To (MRT) are email header fields that tells a mail user agent (MUA) like Thunderbird how to reply to messages which is especially helpful using mailing lists.

Introduction: How MUAs reply to email messages

MUAs have (at least) two reply functions: reply-to-author and reply-to-all.

If you reply-to-author, your MUA creates a new message and sets the To header to the original message's From header. If the original message contains a Reply-To header, your MUA uses its content instead of From. This way the original message's author can tell you to reply to another address if he wants to get replies there.

If you reply-to-all, your MUA creates a new message and sets the To header like above. Additionally it sets the new messages Cc header to the list of all recipients (To+Cc) of the original message, probably excluding your own address.

All these things work pretty well so far, but problems arise with mailing lists:

Introduction: Reply problems with mailing lists

TODO

The solution

TODO

Configure Thunderbird

TODO

Mail-Followup-To and Mail-Reply-To header fields were proposed by Dan Bernstein