1. Avoid publishing your email address on any web page and forums where they have complete control over your privacy.
2. Always mark an unwanted email as spam.
Email services like Hotmail or Gmail create a filter to automatically detect all emails that are spam and then they file a complaint to the network which sent the email. If there are many complaints generated by a sender, your email service will block it completely.
3. Do not enter your email address on websites, and companies that you are unfamiliar with or have a reason to distrust.
You do not give your phone number or home address to a stranger, the same rationale applies to email addresses.
4. Unsubscribe from emails you do not want to receive. Please keep in mind that a good email marketing company will ensure that its subscribers have options to unsubscribe from all headers and footers in the press.