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Correct response to breaking forwarding loop?

1998-02-06 03:59:46
    What is the "proper" handling of a mail message that is not
auto-forwarded because of loop detection?  There may not be a local
mailbox associated with the account with the auto-forward (e.g., the
customer uses it only as a relayer), so that's not a delivery option.
I figure I have four alternatives:

1.  Don't bother with loop detection and let sendmail return an error
    554 when its hop count is exceeded.

2.  Drop the message into /dev/null on the assumption that it is
    probably machine-generated, and that at least one copy has already
    been forwarded to the recipient.

3.  Attempt to send a non-delivery notification to the original sender.

4.  Attempt to send a non-delivery notification to the postmaster.

    #4 might be useful if the customer checks the postmaster mailbox.
#3 can be tricky if you don't want to trust the headers, and otherwise
could result in more looping traffic.  #2 seems palatable if you don't
mind mail disappearing into the void after sendmail returns a
successful delivery notice.  #1 is the simplest as far as procmail is
concerned, but it ends up being like #2 if sendmail doesn't have
anywhere to send the 554.  Suggestions?
-- 
Brian Tao (BT300, taob(_at_)netcom(_dot_)ca)
"Though this be madness, yet there is method in't"

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