Correct email headers for delivering mailing list mail

Question

I\'m writing an application that allows users to send email to dynamically-created mailing lists. For example, a user can send an email to my-team@site.com (the site is a le

Answer 1

Looks like OpenDKIM always uses the From: header so you have to resort to just signing all your emails. See this for instructions.

Answer 2

From: and To: headers are for 'display purposes' (this is what is presented in the users email application as sender and recipient). They don't have to match to the real sender/recipient of a email message which are called "envelope sender"/"envelope recipient" and are specified in the smtp protocol ("MAIL FROM:...." "RCPT TO...").

Example:

Mail comes from alice@example.com, goes to list@example.org and is being delivered to bob@example.net:

From Alice to The list Server:

Envelope Sender: alice@example.com
Envelope Recipient: list@example.org
From Header: alice@example.com
To Header: list@example.org

From the list Server to bob:

Envelope Sender: list-bounces@example.org (so error messages go to the list server, not to alice!)
Envelope Recipient: bob@example.net
From Header: alice@example.com (Bob sees Alice as the sender, this is not modified by the list server)
To Header: list@example.org (again, not modified by the list server)

Optional: Reply-To header: list@example.org (So, if bob presses reply, the reply goes to the list - added by the list server ) - beware: some people do not like reply-to header munging

Additional headers:

Some email clients also understand these additional headers and present special mailinglist features to the user:

• list-Id
• list-Post
• list-help
• list-unsubscribe
• list-owner

https://www.ietf.org/rfc/rfc2919.txt https://www.ietf.org/rfc/rfc2369.txt

Also, you could add a header

Precedence: bulk

which for example tells intelligent out-of-office implementations not to send out-of-office replies to the list. But this is discouraged by RFC 2076.