If a study by a Cambridge researcher is accurate, email addresses with less common first letters get less spam than those with more common ones.

Richard Clayton who conducted the study (and shares his findings in this PDF), titled his research paper "Do Zebras get more Spam than Aardvarks?" Zebras and Aardvarks reprsent email addresses that begin with the letters Z and A respectively, though Clayton made clear that it is not about the two being at opposite sides of the alphabet. It's about how common the letters are.

To answer the question, no. Zebras do not get more spam than aardvarks. They get far less. This is true, at least for the real zebras - the "Z" addresses that actually exist (spammers send to tons and tons of email addresses including ones that don't exist). Aardvarks get a whole lot of it. As do Moles, Snakes, and Penguins (I made up these representations).
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Wow... that's really interesting! I never would have thought to even look into that. Thanks elgato!