The next time you go to create an email address, you might want to consider the first letter a little more carefully than usual. A study of over 500 million junk email messages by University of Cambridge computer scientist Dr Richard Clayton has revealed that certain starting letters attract a higher proportion of spam. For example, addresses starting with "A" ,"M", "S", "R" and "P" accumulated around 40% spam, while those beginning with "Q", "Y" or "Z" got considerably less (about 20%). Dr Clayton believes the differences in spam numbers could be explained by the way spammers generate the e-mail addresses they send junk mail to. Dictionary attacks (a popular method) commonly re-use common names, which are more likely to start with certain letters. Strangely, the study also showed the starting letter "U" getting more than 50% spam, something that Dr Clayton said would require further research.