Would you know how to reject invalid emails in Exchange 2003 Server?

By default the "Recipient Filter" is not disabled in Exchange Server 2003. To prevent unwanted emails not listed in your Active Directory, here's what you need to do.

• Open the ESM (Exchange System Manager) exchange management tool
• In Global Settings, right click on Message Delivery, then select Properties.
• In Message Delivery Properties, click Recipient Filtering tab.
• Put check on "Filter recipients who are not in the Directory">

Well you're not done yet, that's one part only. If you are not using a third-party anti-spam tools, you need to check your SMTP protocol setting. Here's how to:

• In ESM, go to Administrative Groups, First Administrative Group
• Expand Servers, then SERVER name.
• Expand Protocols, SMTP, right click on "Default SMTP Virtual Server" then Properties.
• In Default SMTP Virtual Server Properties, click Advance.
• In Advanced, click Edit
• Put check in "Apply Recipient Filter.

You don't need to restart your Exchange Server, now go check your anti-spam logs if traffic improve for your emails.

For Exchange Server 2007, I suggest you read this article from interjuncture.com website. Post comments or suggestions.

For Email Outsourcing Solution using Google Apps, please visit http://www.moscom.com/apps/ website for more details.