email - Adding mail header if postfix DNS based RBL (realtime black hole) check fails

I have setup a receiving Postfix mail server. Here i have custom code written that parses the whole mail received by postfix and use the headers, body and attachments separately for different uses.

I have currently added SPF and DKIM checks in postfix that result in appending of their results in the mail header to indicate about the character of the mail.

Also i am planning to implement postfix anti-UCE features using DNS based Real time black hole lists (DNSRBL), for this i have added the following:

'smtpd_recipient_restrictions = reject_rbl_client zen.spamhaus.org, reject_rbl_client bl.spamcop.net'

in my Postfix's main.cf file.

My question is, how can I append the results of this check inside the mail headers that are being received?

Thanks in advance!!!

Ashish

Answer

Could you extend your custom parsing to programatically query the RBL in question and then handle the response? i.e., pass the sending address to the RBL, get response, add X- header.

You'd probably want to turn off the smtpd_recipient restrictions if you did this just to reduce the number of hits against the RBL servers.