We are trying to adjust a server so that email will work in conjunction with a spam filter by RedCondor (http://www.redcondor.com). Basically how it works is that you set the MX record to smtp1.redcondor.com, and all email is sent to their server. From there, it is filtered, and then returned back to the originating server (which in this case, it is of course running cPanel). Everything as far as the email getting sent to RC and filtered works fine, but when it is returned it is then rejected by the server. The error is as follows: Does anybody have any suggestions on how to get around this problem? Thanks!