For the last two weeks, after we rebooted our Exchange 5.5 server, we were unable to receive inbound e-mail. However, we could send emails and we had interoffice e-mail. The NDR states the following: The following address had permanent fatal errors - (ccn@xxxxxxxx) ...while talking with mail.tpgl.com: >>>RCPT To:<ccn@xxxxxxxx> <<<550 Unable to relay for ccn@xxxxxxxx 550 <ccn@xxxxxxxx>...User unknown After I reboot the Exchange server, ISA server and stop and restart the IMS service and SMTP service on Exchange numerous times, we will suddenly start to get inbound e-mails again. It's a mystery to me. Thanks for any advice or suggestions! Tina Newhouse