RE: Why do we receive lot of spam emails and how to avoid them?

There really isn't a good way to protect a email address. So, the best solution is to have multiple email addresses and to abandon the addresses that get compromised.

Set your email browser so that it doesn't show images. Spammers use the images to track the emails. Never click on links in unsolicited emails.

Do not press the "unsubscribe" button on unsolicited email as spammers use the unsubscribe button to verify that an address is active.

BTW, it is also good to check the headers of suspicious emails. It is possible for spammers to forge the return address.