title: Format of EML files used by System.Net.Mail.MailMessage and Microsoft SMTP Server
body: <p>I'm trying to wrap my head around the EML files I see generated by System.Net.Mail.MailMessage and generated or consumed by Microsoft's SMTP Server.  I've been reading RFCs 5322 and 5321 and I'm trying to make sense of the format.</p>
  
  <p>Granted, the majority of the EML files I see are adherent to the message format described in 5322 (or 2322 or 822, however good MS stuck to the standards, I don't know).  However, I can't quite decide if the top portion of the file (the X-Sender and X-Receiver lines) constitute the "envelope" as described by 5321.</p>
  
  <p>I guess my questions are:</p>
  
  <ol>
  <li>Is there documentation for the portion of this file with X-Sender/X-Receiver lines (above the message contents)?</li>
  <li>Are there other "commands" that can be expected in this section?</li>
  <li>Is this a "standard" across the board?  i.e. can I expect an EML file that is generated by System.Net.Mail.MailMessage to be parsed correctly in any standard SMTP server?</li>
  </ol>