Microsoft Exchange Rejecting Email with 530 Client was not Authenticated
If you are setting up a new Microsoft Exchange 2007 mail server for use with The Email Laundry, you will need to configure the Exchange server to allow The Email Laundry mail servers connect into your server in order to send email to your domain.
By default, Microsoft Exchange 2007 will reject un-authenticated/anonymous connections. This default behavior will result in the following rejection errors to anyone trying to send email to users in your organisation:
530 Client was not authenticated
To allow The Email Laundry mail servers connect into your server to send email to your domain, you will need to make changes to the receive connectors in Exchange.
Open up the Exchange Management Console > Server Configuration > Hub Transport > Receive Connectors
Right click on ‘Default MAIL’ and select Properties.
Click on Permission Groups and tick ‘Anonymous users’ box. Click on OK.
The last step is to restart the Microsoft Exchange Transport service.
This change will allow The Email Laundry servers connect into your Exchange server and relay email to your domain.
For additional security, SMTP traffic into your Exchange server should be restricted to The Email Laundry servers. This can be put in place at the firewall level before SMTP traffic gets to your Exchange server or on the Exchange server itself. The benefits of this are to prevent direct-delivery spam and Denial of Service attacks on your Exchange server.