RBL Query Before Sending

[kharford]

Hi,
Is there a way to check if a spool's internet IP is listed on an RBL list before trying to send it out. And if there is a way to do this, would it be possible to relay that message to another spool with a different internet IP within postfix?

I am having issues with a RBL that is having issues listing my IP's every so often through no fault of my own.

Thanks

 

[Noway2]

In Postfix you can use the "check_rbl_client" option. This command automatically uses the standard DNS reverse octet query and if a record is found, it indicates that the client is on a list. You could use it on the receiving side, which is typical to block spam or you could deny sending. As with most Postfix options, the behavior will depend upon which restriction section you place them in.

A full example (for spam blocking), including checks would be:

smtpd_recipient_restrictions =
   reject_rbl_client zen.spamhaus.org
   reject_rbl_client bl.spamcop.net
   permit_mynetworks
   check_policy_service inet:127.0.0.1:60000
   permit_sasl_authenticated
   permit_mx_backup
   reject_unauth_destination
   reject_unknown_recipient_domain
   permit

If you are looking to see if your domain / IP is being listed, you can try any of the diagnostics services out there. I typically like mxtoolbox, but Spamhaus's zen will cover quite a few as will Sorbs (which tends to be amongst the pickiest) which I think is mostly a concatenation of different RBLs instead of a unique list.

 

[kharford]

Thanks for your response!!

If I do implement the check_rbl_client on the sending side, is it possible to not bounce the message but re-inject into postfix and deliver from a different internet IP?

Thanks again Noway2!!