Thanks for taking the time to look, I really appreciate it!
Not sure what I missed but these are the steps I've taken.
I added the domain to postini.
Updated the MX records to point to postini (domain.com.s8a1.psmtp.com.......)
Added the domain as an accepted domain to our exchange hub.
Add the domain to my inbox.
When trying to send to this it keeps bouncing back.
Here is the SMTP test I did at www.testexchangeconnectivity.com
Testing inbound SMTP mail flow for domain user@domain.com.
The Microsoft Connectivity Analyzer failed to test inbound SMTP mail flow.
Test Steps
Attempting to retrieve DNS MX records for domain domain.com.
One or more MX records were successfully retrieved from DNS.
Additional Details
Testing Mail Exchanger domain.com.s8a1.psmtp.com.
One or more SMTP tests failed for this Mail Exchanger.
Test Steps
Attempting to resolve the host name domain.com.s8a1.psmtp.com in DNS.
The host name resolved successfully.
Additional Details
Testing TCP port 25 on host domain.com.s8a1.psmtp.com to ensure it's listening and open.
The port was opened successfully.
Additional Details
Analyzing SMTP Capabilities for server domain.com.s8a1.psmtp.com:25
The test passed with some warnings encountered. Please expand the additional details.
Additional Details
Attempting to send a test email message to user@domain.com using MX domain.com.s8a1.psmtp.com.
Delivery of the test email message failed.
Additional Details
The server returned status code 550 - Mailbox unavailable. The server response was: 5.7.1 Unable to relay
Exception details:
Message: Mailbox unavailable. The server response was: 5.7.1 Unable to relay
Type: System.Net.Mail.SmtpFailedRecipientException
Stack trace:
at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Microsoft.Exchange.Tools.ExRca.Tests.SmtpMessageTest.PerformTestReally()