Exchange smtp queue filling up rapidly

I am running Exchange 2003 on Server Standard 2003 and I keep having to clean out the smtp connector queue inorder for my email to function properly(i.e. sending emial to external recipients) the queue keeps filling up with the address postmaster@center.local. We have enabled the recipient filters, gotten rid of all unnesaccary connectors, we have also deleted all un-needed mailboxes and users, and recently rebuilt the server(reformat). I need to get the issue with the smtp connector queue resolved in that I need to get it to not fill up and cause the smtp errors that it is causing any assistance with this matter would be appriciated