Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am implementing a blacklist filter for a SMTP relay, which allows the user to define rules based on sender email, receiver email, sender ip or a combination of these. What SMTP status code should it reply if the email gets blocked because it is found to be blacklisted?

share|improve this question
up vote 1 down vote accepted

Postfix defaults to handle reject_rbl_client blacklists by sending a 554 (Transaction failed) together with a textual explanation. A google search also suggest that being a rather common practice in dealing with blacklists.

share|improve this answer
I will use "554 5.7.1. Blacklisted" – Tom Jul 21 '10 at 9:28

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.