On 13/02/2014 09:46, template.mob...@gmx.de wrote:
Hi,
i'm using postfix in our small company successfully for many years.
But now a problem arised and I was not able to solve it myself or
with help from the docs.
We are using sender_bcc_maps, because we want any mail that is sent
from one of our employees to be copied to a central mail account.
Since a few month our mail provider delivers us mails that are
addressed to one of our employees, where the return-path header ist
set to the mail address of the receiving employee. The mail is now
copied to our central outgoing account. We don't want that.
Well, setting the return path header to be the same as the recipient is
wrong, and stupid. So if this is being done by your mail provider then
you need to complain to them, raising a fault report if necessary
(because this is a fault, and a serious one), in order to get the
problem resolved. But it's also possible that it's being done by the
original sender of the email, in which case the chances are that it's
simply spam, since this is a common trick of spammers to try to get
round filters.
How does the sender_bcc_maps mechanism exactly works? Does it react
on mail body header fields like return-path? Is it in detailed
documented somewhere? Can we prevent sender_bcc_maps from reacting on
the return-path field?
http://www.postfix.org/postconf.5.html lists the order in which Postfix
determines the sender for the purposes of bcc_sender_maps:
1. Look up the "user+extens...@domain.tld" address including the
optional address extension.
2. Look up the "u...@domain.tld" address without the optional address
extension.
3. Look up the "user+extension" address local part when the sender
domain equals $myorigin, $mydestination, $inet_interfaces or
$proxy_interfaces.
4. Look up the "user" address local part when the sender domain equals
$myorigin, $mydestination, $inet_interfaces or $proxy_interfaces.
5. Look up the "@domain.tld" part.
If not, how can our problem be solved? Should we use some kind of
filter for incoming mails that removes the return-path?
If it isn't being caused by a fault at your mail provider, then I'd be
inclined to simply reject anything where the sender or return path
address is the same as the recipient. The chances are greater than 99%
that it's spam. And if it isn't, someone sending mail out that's so
badly configured doesn't deserve to have it delivered.
Mark
--
My blog: http://mark.goodge.co.uk
