In your second example, there are multiple recipients in the same SMTP transaction, since you're sending to both an external destination and a local destination in your message. It's a tricky example because the DH mail server is (in this case) both accepting the mail from you (as an authenticated client), and delivering it locally. So your mail client is sending RCPT TO for both; the mail server is queuing the one for an external destination and sending it out (probably with a different queue-id) and delivering yours to its final destination (your mailbox). Same deal - multiple envelope-recipients in the original SMTP transaction opening up a connection to the DH mail server.
The second case seems (AFAICT) to have only a single recipient - you.
But again, I'd try looking at messages from outside sources - and in those cases, it can be very hard to tell if there were multiple recipients or not (unless you are the sender).
You could do some experiments by sending yourself messages to different addresses at domains you host from an outside account (e.g., hotmail, gmail) - if you CC or BCC multiple recipients, you should not see that "for..." info in the Received line; if you send to a single recipient, you should see it.