Why is postfix accepting and bouncing over quota accounts instead of rejecting?

[HostaHost]

Postfix with Plesk 11 appears to accept messages for accounts, even if they're over their quota, and then generates a bounce back; as opposed to simply rejecting the message to begin with. This is causing blacklisting issues. What config needs to be changed to prevent this?

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<user@domain>: Mail quota exceeded

 

[IgorG]

Look at this article - http://kb.parallels.com/115395

 

[HostaHost]

Thank you!

 

[HostaHost]

I had time to look through this today. I think you misunderstood what I'm seeing happen. On our Plesk 11 Postfix servers, messages to accounts that are over quota are being accepted from the remote SMTP sending server, then a bounce message sent back to that sender (or to an innocent victim in the case of a forged sender on a spam message).

In http://kb.parallels.com/115395, it sounds like our servers are not behaving as expected. The article makes it sound like what should be happening when an account is over quota is that the incoming SMTP attempt from the sending server should be responded to with a 4.x.x status rejection and the message refused for the sender to try again later. The article then goes on to tell you how to update that response to a 5.x.x permanent rejection instead. In our case, I'm not seeing the servers issue a 4.x.x rejection to begin with, they accept the message and then generate an outbound bounce message from mailer-daemon with the contents I quoted in the first post.