<div>
Further investigation (after following NRhode's advise) found that MX records were correct but Mimecast was blocking the trnasmission.
</div>


Further investigation (after following NRhode's advise) found that MX records were correct but Mimecast was blocking the trnasmission.

<div>
<div class="content wysiwyg-content">
I have a sub-tenenat, CLF, that has shared my Exchange 2007 Server for some time. &nbsp;They are now moving out and I have migrated their email to a hosted Exchange account and changed their MX records. &nbsp;They are able to send and receive emails on that new server just fine with the exception of emails to and from my Exchange server (their old one). &nbsp;I know I have got to be missing something but can't figure it out. &nbsp;<br />
<br />
Once I verified their new email was working properly, I have performed the following tasks on my Exchange server:<br />
<br />
&nbsp;•Removed their domain from Organization Configuration &gt;&nbsp;Hub Transport &gt;&nbsp;Accepted Domains<br />
•Removed the email addresses from individual accounts<br />
<br />
Is there anything else I need to do?
</div>
</div>


I have a sub-tenenat, CLF, that has shared my Exchange 2007 Server for some time.  They are now moving out and I have migrated their email to a hosted Exchange account and changed their MX records.  They are able to send and receive emails on that new server just fine with the exception of emails to and from my Exchange server (their old one).  I know I have got to be missing something but can't figure it out.  

Once I verified their new email was working properly, I have performed the following tasks on my Exchange server:

 •Removed their domain from Organization Configuration > Hub Transport > Accepted Domains
•Removed the email addresses from individual accounts

Is there anything else I need to do?

Remove a domain from Exchange 2007

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.