title: filter email with attachment using mimekit/mailkit
body: <p>is there a way to filter emails with attachments only?
  I'm using this code</p>
  
  <pre><code>using (var client = new ImapClient())
         {
           client.Connect(IMAPServer, IMAPport, IMAPSSL);
           client.AuthenticationMechanisms.Remove("XOAUTH2");
           client.Authenticate(User, Password);
           var inbox = client.Inbox;
           inbox.Open(FolderAccess.ReadOnly);
           //filter email with attachments only
             var results = inbox.Search(SearchQuery.NotSeen.And(SearchQuery.NotDeleted));
    }
  </code></pre>