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Re: Bounce/System Notification Address Verification

2005-06-29 22:48:07

At 08:02 -0400 on 06/29/2005, Bruce Lilly wrote about Re: Bounce/System Notification Address Verification:

On Wed June 29 2005 00:30, Robert A. Rosenberg wrote:

 At 13:50 +0100 on 06/28/2005, Tony Finch wrote about Re:
 Bounce/System Notification Address Verification:

 >However if the return path might have been an alias which expands to more
 >than one address, and this can reslult in legitimate bounces with more
 >than one recipient.

 No it doesn't. The original message has ONE recipient (the alias) and
 gets delivered to it. At that point the alias gets expanded and
 creates a new message which is sent to each recipient. Unless 2 or
 more recipients are hosted at some domain other than the one where
 the alias is hosted, each copy is delivered directly to their mailbox
 (as if the message had arrived with all the addresses explicitly
 listed as RCPT-TOs).

You might want to reread Tony's statement carefully.  Perhaps an
example will help:

Original message:
Return-Path: admin-group(_at_)example(_dot_)net

Return-Path: <>
To: admin-group(_at_)example(_dot_)net

which may well be expanded to multiple RCPT TO mailboxes.

... at the receiving end AFTER reception. It comes in as ONE address and when delivery is attempted, the message is cloned for delivery to multiple addresses/mailboxes. As I stated, unless the expansion creates a list that has 2 or more addresses that are NOT handled by THIS SMTP Server, you get the same result as if all the addresses were listed in the original message. Only in the "2 or more addresses that are NOT handled by THIS SMTP Server" case can you end up with a message that is relayed with more than one RCPT-TO (with a MAIL-FROM of <>) and that only when 2 or more of these addresses are in the same domain (or at least have domains that map to the same MX server).

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