Original setup as follows: Web and MX record pointed to: 22.214.171.124 for stingray-webdesign.com All email addresses work fine there. Then: Installed a new instance of ispconfig at 126.96.36.199. Pointed Web and MX record to 188.8.131.52. Now all my emails get bounced back to me stating: The following recipient(s) could not be reached: email@example.com on 2/5/2007 3:49 PM The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address. <smail.lasalletown.com #5.1.1 smtp;550 5.1.1 <firstname.lastname@example.org>: Recipient address rejected: User unknown in local recipient table> I have other domains running at 184.108.40.206 and I have no problems with the emails with them, only with this domain. This specific domain is the host of the ISPConfig server (webserver.stingray-webdesign.com). For example you can email email@example.com and have a successful send, but when you email firstname.lastname@example.org your email will be bounced back.