Tod1d's Thought Process

Problem

I am attempting to send email using the localhost mail server in IIS. However I receive the following error message:

Exception type: SmtpFailedRecipientException
Exception message: Mailbox unavailable. The server response was: 5.7.1 Unable to relay for tod@kahunaworld.com

Solution

I received this error on my local staging server, so I had access to the server via Remote Desktop. I am not sure how "secure" this solution is, so use at your own risk.

1. Open IIS.
2. Right click on "Default SMTP Virtual Server" and select "Properties".
   
3. Select the "Access" tab and click on the "Relay" button. This opens the Relay Restrictions window.
4. Select the "All except the list below" radio button.
5. Remove all items from the "list below".
6. Check the checkbox for "Allow all computers which successfully authenticate...".
7. Click OK.
8. Click on the "Authentication" button. This should open the Authentication window.
9. Make sure that only "Anonymous access" is checked.
10. Click OK.
11. Click OK again.