You may not believe in Santa Claus, but surely you must believe in Wikipedia, and that's enough to read this post.
According to Wikipedia roughly 33% of the World's population are Christians, the World's population is currently around 6.6 billion, and the average life expectancy is 67 years. Let's assume that 80% of children believe in Santa Claus and on average stop writing to Santa Claus at around 12 years old. Now let's assume that 50% send an email to Santa requesting a new train-set or pony.
The number of emails Santa Claus will receive this year is (6.6 billion * 0.33 * 12/67 * 0.80 * 0.50) approximately 150 million emails from excited children. That's a lot of emails! Now let's assume that poor old Santa Claus has been too busy reading emails to install an email security solution (note: link outdated). Since his email address is so well known (santa AT thenorthpole DOT com) and the spammers, who believe in him, know he reads all his email, he'll likely be receiving over a 90% spam rate.
If only 10% are legitimate email, he'll be looking at 1.5 billion emails, 1.35 billion of which are spam!
So as you're getting ready for Christmas, or whichever holiday you celebrate, spare a thought for Santa Claus.