Read Part 1 of Fighting Spam
According to the MX Logic Threat Center almost 80% of the emails on the internet is SPAM. Some of it undoubtedly will find its way to your mailbox. Your ISP / Email provider may put in several measures to reduce this spam, but you may still find yourself fighting spam!
Note: Most of the items below are meant for those who have POP / IMAP access to their mailboxes. Wherever applicable, I have mentioned the equivalent if you're using a web based email service such as Hotmail / Yahoo / GMail / AOL / any other paid / free web based mail service.