We are seeing more systems that are rejecting mail that violates the sender's published SPF policy. Mail from a domain with published a SPF policy that we forward on behalf of our customer may violate the sender's SPF policy because the sender has no way to know that the recipient is forwarding mail to another system. The recipient that is forwarding the mail has no way to know in advance that the sender does not wish mail from the their domain to be forwarded.
In most all cases the rejected mail is spam with a forged sender address but we have seen a small percentage of legitimate mail rejected. It is this small percentage that we would like to see accepted by the system that the mail is forwarded to.
The SPF forwarding problem is well known and the debate about wether SPF breaks forwarding or forwarding is inherently broken still rages on.
To ensure deliveriablity of mail that is forwarded,
SRS will be enabled
for all forwarded mail. Currently SRS is enabled for mail
forwarded to AOL and a few dozen other systems.
Another problem is that more and more systems are rejecting spam that is forwarded to them. When a system that we are forwarding mail to rejects a message, a Delivery Status Notification must be delivered to the sender. If the rejected message is truly spam, and it almost always is, the sender is most likely forged and the DSN is sent to the innocent forgery victim adding to the bad and growing backscatter problem.
Another issue with forwarding spam is that many systems pay attention to what IP addresses are sending them spam in the same way that this system does. The recipient system does not know or care that the spam is forwarded on behalf of a customer. To the receiving system the message is just spam. Too much spam from an IP address and the IP address is blocked. Blame the spammers, not the mail system operators.
To reduce the backscatter that this system generates and to reduce the possibility of our forwarding servers being blocked and preventing mail from being forwarded, messages with a spam score of 6.0 and higher will no longer be forwarded. This change has been in affect for mail to AOL and its subsidiaries since May 2005 with no customer complaints.
Starting today messages scoring 6.0 and over will not be forwarded to adelphia.net, yausi.com, yahoo.com, hotmail.com and cox.net. SRS envelope sender re-writing is also being applied to mail forwarded to those domains.
Along with this change is a real-time report showing forwarded messages that have been discarded.
To: email@example.com recipient@domain-hosted-here 1 18.2 firstname.lastname@example.org 1 28.5 email@example.com 1 20.3 firstname.lastname@example.org 1 15.5 email@example.com 1 12.5 firstname.lastname@example.org 1 18.2 email@example.com 1 12.5 firstname.lastname@example.org 1 23.9 email@example.comSelect Account -> Real-Time Reports -> Forwarded Discards to view the reports for your account.