A client of ours who subscribes to our Spam Filtering service recently reported that a message from a vendor of theirs was rejected. We checked our message audit logs and discovered that the message in question was tested by our service and forwarded normally to their Exchange 2007 server.
Further investigation revealed that the message was rejected by their Microsoft Exchange 2007 server’s Anti-Spam feature with message:
550 5.7.1 message rejected as spam by content filtering.
Since we are filtering their e-mail, they no longer need the Anti-Spam services of the Exchange Server, so here is how we disabled it.
- Launch the Exchange Management Console
- Expand Organization Configuration
- Choose Hub Transport
- Select the Anti-Spam tab
- Highlight each feature (except recipient filtering), right click on it and then click “Disable.”
- We left Recipient filter enabled because it is meant to prevent reverse NDR attacks.