title: Error in getting sender's certificate for Outlook VSTO solution
body: <p>While working on Outlook VSTO solution, facing an issue for getting email sender's certificate (PR_USER_X509_CERTIFICATE) when PR_ADDRTYPE_W is  SMTP whereas in case of EX i.e. EXCHANGE no exception thrown for below code.</p>
  <p>Here is my sample code of C# to get user certificate</p>
  <pre><code>NameSpace mapiNamespace = mailItem.Application.GetNamespace(&quot;MAPI&quot;);
  Recipient emailSender = mapiNamespace.CreateRecipient(mailItem.SenderEmailAddress);
  emailSender.Resolve(); 
   
  object[] senderCertificateInfo = emailSender.PropertyAccessor.GetProperty(&quot;http://schemas.microsoft.com/mapi/proptag/0x3A701102&quot;);
  </code></pre>
  <p>I have analyzed the difference of both types of emails via OutlookSpy. As per my findings,  for EXCHANGE lot of additional properties are also available with PR_USER_X509_CERTIFICATE but for SMTP, a very few properties available as compare of EXCHANGE emails.</p>
  <p>Can someone assist me to get sender certificate for all cases?</p>
  <p>Thanks</p>