Perhaps I do have a dated perception.   Think of when we had to filter our own spam with rules, and articles like <a href="http://www.pcworld.com/article/111193/stupid_spam_tricks.html" rel="nofollow">http://www.pcworld.com/article/111193/stupid_spam_tricks.htm...</a> were in vogue (link from 2003, 1st link in the search).  Note that the first 2 "tricks" this PCWorld article mentions are misspellings and the "bogus" use of "Re:".  Maybe I'm still stuck in those days, but I still associate these tricks with spammy mail.