I have just started receiving the following error while trying to send to one particular domain. We have sent to this domain in the past. It just started today. The following recipient(s) cannot be reached: jhiggins@otherdomain.com on 5/13/2008 10:56 AM You do not have permission to send to this recipient. For assistance, contact your system administrator. <mail.mydomain.com #5.7.1 smtp;550 5.7.1 jhiggins@otherdomain>... Relaying denied. Proper authentication required. I understand how relay errors occur while trying to send email through one's ISP from another domain; however this seems to be coming from our own Exchanger Server 2003. I had this error a couple of weeks ago to a different domain, again, it appeared out of the blue after having sent emails to that domain. I added all internal IPs to the allowed relay and that seemed to fix it. Any help? Thanks. Mike

Is all the user are not able to send mails to external domain? Please reply the authentication type in your exchange server 1. Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager. 2. In the console tree, expand Servers, expand ServerName, expand Protocols, and then expand SMTP. 3. In the right pane, right-click the SMTP virtual server (for example, Default SMTP VirtualServer), and then click Properties. 4. Click the Access tab. 5. Under Access control, click Authentication. Please reply the authentication type in your exchange server

So far, only one employee and myself are having the problem. There only maybe three employees who would have cause to contact this client. When this happened before, it was a vendor that only two employees needed to email and myself. Authentication types are: Anonymous Basic Windows Integrated The permissions for Windows Integrated are set to "Authenticated Users". I have an SMTP virtual server on another server which processes spam. It is only set to Anonymous. I have sent test emails this morning, but have not received delivery receipts or NDRs. Thanks. Mike