title: smtp;550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1)
body: <p>I'm running Windows server 2008 R2 but am getting smtp mail rejected from a few domains.</p>
  
  <p>To test it I'm dropping a text file into C:\inetpub\mailroot\Pickup directory, with something like this:</p>
  
  <pre><code>From: my@emailaddress.com
  To: someone@somewhere.com
  Subject: testing
  
  This is a test
  </code></pre>
  
  <p>It will send to some domains, but some are returning:</p>
  
  <pre><code>Reporting-MTA: dns;DEDICAT-93I3U5A
  Received-From-MTA: dns;DEDICAT-93I3U5A
  Arrival-Date: Wed, 8 Aug 2012 12:50:58 +0100
  
  Final-Recipient: rfc822;someone@somewhere.com
  Action: failed
  Status: 5.5.0
  Diagnostic-Code: smtp;550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1)
  </code></pre>
  
  <p>I understand this could be something to do with the smtp setup on the server (IIS 7.5).
  Can anybody give me some advice as to where to start please?</p>
  
  <p>Thanks,</p>
  
  <p>Andy.</p>