On Monday, October 28, 2002, at 05:46 AM, Alan Summerfield wrote:
I use the router to filter messages using the Return-Path, but suddenly I'mIt is highly recommended that you do not block based on this criteria. If you do, your users will not receive _any_ bounce notifications or other messages actually sent by other MTAs. Using blacklists might be an acceptable alternative. As I don't use them, I'll leave that to others.
getting messages (supposedly from Postmasters and MAILER-DAEMONs but clearly
SPAM) where the first line is:
Return-Path: <>
What can I enter to block such messages?
Tim
Here are some relevant excerpts from RFC 2821. Notice the MUST requirement for forming the notification:
3.7 Relaying
...
One way to prevent loops in error reporting is to specify a null
reverse-path in the MAIL command of a notification message. When
such a message is transmitted the reverse-path MUST be set to null
(see section 4.5.5 for additional discussion). A MAIL command with
a null reverse-path appears as follows:
MAIL FROM:<>
...
6.1 Reliable Delivery and Replies by Email
...
If there is a delivery failure after acceptance of a message, the
receiver-SMTP MUST formulate and mail a notification message. This
notification MUST be sent using a null ("<>") reverse path in the
envelope....
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