Many spammers harvest email addresses from websites. You should not place your email address on your website in the format of mailto:[email protected]. This is a sure way to increase SPAM. The best method is to put in on your site in the format of myemail at domain.com, or use a contact form which has your email address hidden.
A second method os to turn off your catch-all email account. Spammers will sometimes to dictionary attacks on a domain name and randomly send it to non-existant email accounts on your domain name.