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Ive got some issue with email forwarding. Through the ISPConfig 3.0 i've set some email forwards. When I'm trying to send the email on the forward address daemon is returning the message with error 521, which mean that message is spam. But on the second hand, when i'm trying to send the email direct on the address without the forward - the same topic and content - the email easly go to the inbox. Where can be the problem? Whole error message:

<> (expanded from <>): host[] said: 553 5.3.0 nlpi147 DNSBL:ATTRBL 521< ..*.* >_is_blocked.__For_information_see_ (in reply to MAIL FROM command)

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up vote 1 down vote accepted

Some of the hosts involved are apparently listed on a black list (DNSBL).

I can't tell from your description what you tried to send how from where, but one of the hosts involved in the failed attempt is listed for whatever reason in some black list.

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Okay, see you are right, i've checked the DNSB List and found that host is on SpamCannibal list because of invalid PTR record. So making a PTR record for mail dns records should be helpful in this case? – Kamil Dec 2 '11 at 10:20
If this is indeed the only reason for the listing, it should be sufficient, but I guess you will have to wait until the listing expires or somehow contact them to remove your entry. – Sven Dec 2 '11 at 10:36
It would be easier if my IP was banned, but it's whole OVH.. great =) – Kamil Dec 2 '11 at 10:51
If the host has a dynamic IP address, it won't be able to get of some blacklists. As per the RFCs it needs a static address. Many ISPs have provided lists of dynamic addresses so that they can be blacklisted and not used to send spam. – BillThor Dec 2 '11 at 13:15

DNSBL:ATTRBL 521< ... >_is_blocked.__For_information_see_

This is a DNSBL (client) blacklist response.
It has nothing to do with addresses, i.e. nothing from that machine will be accepted by

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