Salut,
In order to avoid bounces which possibly attract SPAM, it is imperative
nowadays for a relaying mail server (e.g. backup MX) to verify the
existence of the recipient before attempting delivery of the mail.
Postfix already offers a facility to achieve this.
However, currently, it is not possible for Postfix to behave
differently in the two situations "Recipient does not exist" and
"Recipient cannot be verified". Thus, if mails are rejected in case the
recipient does not exist, it is not possible to reject them in case the
mail server does not respond.
We (René Nussbaumer and me) worked on a patch to correct this behavior
by introducing configuration parameters which regulate this behavior. A
Backup MX, for example, should accept mail if the main MX is not
available, so it should not create an error message. If the main MX is
avialable, however, only mail for existent mail accounts should be
collected.
I created the appended patch for postfix in pkgsrc to fix the problem.
It adds the new configuration parameters while not affecting the
default behavior. It was also contributed upstream:
http://archives.neohapsis.com/archives/postfix/2008-04/1309.html
http://archives.neohapsis.com/archives/postfix/2008-04/1311.html
Martti, is that ok for you? I would consider it unbelievably helpful
for many MX setups if this patch could be shipped by default unless
upstream releases a new package which has it.
Tonnerre
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