I'm running SharePoint 2007 on a Windows 2003R2 machine with SMTP role installed (no Exchange). I'm having trouble with configuring the SMTP service in a secure way. I've followed the guide on http://technet.microsoft.com/en-us/library/cc262947(office.12).aspx , which advices to set the mail server as an open relay. This causes problems with security (thousands of unknown emails appear in my inetpub/mailroot/queue directory). My SharePoint Incoming E-Mail Configuration is done without SharePoint Directory Management Service and in settings mode set to Automatic. Whenever I attempt to make the SMTP server more secure I end with either incoming or outgoing mail not working. Here is the exact configuration of my SMTP server: *Default SMTP Virtual Server Properties* **Access** Access control => Authentication: Anonymous access Secure communication - no certificate assigned Connection control: none Relay restrictions: none **Delivery** Outbound Security: anonymous accecss **Security** operators: administrators, nt authority\local service, nt authority\network service What should I do to make my SMTP server more secure (and avoid unwanted messages) without losing incoming/outgoing e-mail functionality in SharePoint?

Change your relay restrictions to the IP of the SharePoint server sending email.http://sharepoint.nauplius.net

This has indeed solved my problem, thank you for help!