Some of the major technology companies already have the tools to gather information about you, without your permission. Despite some sources, I personally would not doubt the ability of Robots to probe your email program for your email address. One way is to avoid using your own personal email address on Web sites, and instead use one specifically for the purpose. This way you protect your one personal email address and you only receive junk emails on the one email account rather than several. Another way is when you are leaving your email address for a subscription or a news article or daily horoscope, always use an email address that is specifically for that purpose.
Email filters are also available in some email programs to sift through unsolicited junk mail.
There are also software programs that you can buy that will do the same. If you have young children around, Internet usage must be monitored carefully by adults at all times. Content filtering software can be purchased as well. The most effective prevention is not always the best, as someone or a group of email users will be affected in some way. Some email filters will do a darn good job, but at the sacrifice of filtering out legitimate emails.