First of all, I wonder if we shouldn't be stripping the Return-Receipt-To header from incoming mail. If we don't, we should at least understand what to do with a receipt, like the following:
To: mlist-listname@example.com
Date: Fri, 29 May 2009 18:16:15 +0000
Subject: Delivered: Subject of Email
Content-Type: multipart/report; boundary="part736150-boundary-922218497-1704572214"
MIME-Version: 1.0
--part736150-boundary-922218497-1704572214
Content-Type: text/plain
Your message was delivered to the recipient.
--part736150-boundary-922218497-1704572214
Content-Type: message/delivery-status
Original-Message-ID:1155467857
Final-Recipient:soandso@example.com
Action:Delivered
--part736150-boundary-922218497-1704572214--
First of all, I wonder if we shouldn't be stripping the Return-Receipt-To header from incoming mail. If we don't, we should at least understand what to do with a receipt, like the following: