This is the Lists → Mailing List → Signature/Headers Tab
This tab lets you configure a message signature and header modifiers for mailing list messages sent to list members.
The List Signature is text which is added to the bottom of messages sent to the list members. This is plain text only (no HTML) and could contain information such as how to unsubscribe from the list, or list rules, etc.
Message Header Modifiers indicate modifications which VPOP3 will make to the message header of messages sent to the list members.
The default modifiers are a sensible starting point. You can change the header modifiers to change how replies to list messages are handled, and to remove things like receipt requests or add mailing list header fields.
If this is blank, then no header modifications are made. This means that the list members will receive the same headers that the originator sent (with some control & status headers added by VPOP3 and other mail servers). This may be what you wish, but often it isn't. For instance, replies will go back to the original sender, not to the list, and if the original sender asked for read receipts, then they will receive a receipt from every list member, which may be a lot of receipts.
So, you can tell VPOP3 to change the headers - for instance:
•Reply-to:email@example.com indicates that replies should go back to the 'firstname.lastname@example.org' rather than the original sender.
•Return-Receipt-To: indicates that VPOP3 should remove any 'Return-Receipt-To' headers to help prevent read receipts being generated.
•Precedence: bulk should tell automatic responses not to fire, so that all list members aren't bombarded with out-of-office replies from list members.
If you are configuring a subscription mailing list of some sort, for instance, for discussions, it can be worth adding the standard list header fields, such as List-Unsubscribe and List-Help. See RFC 2369 for details of these header fields, for instance, a header:
can be used to tell the receiving mail software how to generate an email to unsubscribe from the list.
Header modifiers are defined as Header-Field ":" Header-Data
If you want VPOP3 to remove a header field, just specify it as Header-Field ":" without any data
Common email header fields are documented in RFC 2076.