[Fwd: Postfix SMTP server: errors from avalanche.netmar.com[198.69.224.177]]

Can someone tell me if I'm blocking spam here of if I'm somehow blocking
some of the emails from this list?

I'm definitely getting email, but I keep getting these messages popping
up on my servers.  Does anyone know why?

-------- Original Message --------
Return-Path: <double-bounce@cling.tacocat.net>
X-Original-To: postmaster
Delivered-To: postmaster@tacocat.net
Received: by cling.tacocat.net (Postfix)    id 6D9B34C07A; Wed, 16 Jun 2004
19:19:33 -0400 (EDT)
Date: Wed, 16 Jun 2004 19:19:33 -0400 (EDT)
From: MAILER-DAEMON@cling.tacocat.net (Mail Delivery System)
To: postmaster@tacocat.net (Postmaster)
Subject: Postfix SMTP server: errors from
avalanche.netmar.com[198.69.224.177]
Message-Id: <20040616231933.6D9B34C07A@cling.tacocat.net>

Transcript of session follows.

  Out: 220 cling.tacocat.net ESMTP Postfix (Debian/GNU)
  In:  EHLO avalanche.technically-sound.com
  Out: 250-cling.tacocat.net
  Out: 250-PIPELINING
  Out: 250-SIZE 10240000
  Out: 250-VRFY
  Out: 250-ETRN
  Out: 250 8BITMIME
  In:  MAIL FROM:<pgsql-general-owner+M61963@postgresql.org> SIZE=3112
  Out: 250 Ok
  In:  RCPT TO:<tallison@tacocat.net>
  Out: 450 <pgsql-general-owner+M61963@postgresql.org>: Sender address
rejected:
      unverified address: Address verification in progress
  In:  DATA
  Out: 554 Error: no valid recipients
  In:  RSET
  Out: 250 Ok
  In:  QUIT
  Out: 221 Bye