Running 18.104.22.168 isp3 on deb lenny 64 from perfect server setup. I up'd the mysql max_connections and max_user_connections and it's fixed many problems but we do get several of these every so often: warning: mysql:/etc/postfix/mysql-virtual_client.cf: table lookup problem And this is from a known user/domain to known user/domain coming from a remote connection outside the server. The user gets email and the sending user send just fine, but sometimes it happens with different people at differetn times. Right after this is what happens: postfix/smtpd: NOQUEUE: reject: RCPT from adsl-xxx-xxx-xxx-xxx.sip.asm.bellsouth.net[xxx.xxx.xxx.xxx]: 451 4.3.5 <adsl-xxx-xxx-xxx-xxx.sip.asm.bellsouth.net[xxx.xxx.xxx.xxx]>: Client host rejected: Server configuration error; from=<email@example.com> to=<user2@validdomain> proto=ESMTP helo=<User1PC> And the User1 gets a bounceback saying the same. I saw an earlier post where the suggestion was to update isp3, but I'm already on the latest version. Thoughts/tweaks?