title: What is DistinguishedFolderId->Mailbox->EmailAddress in php-ews?
body: <p>I am using a php-ews to access our EWS server. I found an example for creating a calendar event as follows:</p>
  
  <pre><code>$request = new EWSType_CreateItemType();
  $request-&gt;SavedItemFolderId-&gt;DistinguishedFolderId-&gt;Id=EWSType_DistinguishedFolderIdNameType::CALENDAR;
  $request-&gt;SavedItemFolderId-&gt;DistinguishedFolderId-&gt;Mailbox-&gt;EmailAddress = "dude@test.com";
  ...
  </code></pre>
  
  <p>My question: what is <em>DistinguishedFolderId->Mailbox->EmailAddress</em> and what does it do? I know this attribute is optional.</p>