These are all non-guessable addresses used exclusively for dropbox.
All links in that mail point to http://lindXXXbuchleitner.com/wp-content/plugins/wps.php?c002 (XXX = sey), which presumably carries something malicious (I didn't click).
Question to HN: Who else has received this spam?
And question to Dropbox: Why was I not notified when my e-mail addresses (and what else?) were stolen from your servers?