Ok, here's how I'm going to break it down. First, I'll remove all data not essential for email tracking. What's left is:

Now, headers are tacked on in reverse chronological order. So let's seperate, resort, and explain:

This is just your SMTP server evaluating whether or not your email is spam by score. "Brightmail" has given your email a score of 10.34, which means it doesn't consider it spam. This kind of rating tells me this system uses banyesian training to adjust its filter.

Who sent the email to whom, and when.

Now here is the "nitty gritty". You created the email and hit send at 6:01:55pm on the 26th of March. The first external machine to get it was "mac.com" on Sunday, June 3rd at 12:21:56 in its time zone. From there it went to smtpout.mac.com at 12:22:16, then off to mwinf3103.me.freeserve.com at 21:22:18 (different time zone, elapsed time was 2 seconds). It added a second entry for itself again 27 seconds later, most likely after putting it in a different queue. It seems that this server is the one physically hosting your friends' email address, and exactly 0 seconds later, put the final entry in the header to say the email was delivered.