Report: Spam Ratio Depends on Address’s First Letter
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).
M, S, and P are some of the most common letters that begin email addresses, and incidentally, 42% of messages to these addresses are spam. Addresses that begin with less common letters like X or Q get a significantly less percentage of spam.
To gather his data, Clayton went through UK ISP, Demon Internet. The ISP uses a spam detection system from Cloudmark, and only email messages that reached that system were considered for the study.