How to Identify Spammy Email Headers
Spam that is sent from most sources won´t harm your computer and is strictly used for advertising purposes. There is, however, some spam emails that have viruses attached to them. These viruses (or sometimes worms, depending on the spam) can do a number of things to your computer. Some of them are designed to destroy your computer; others are designed to search through your computer in order to ferret out personal information. While there are laws against spam, there is really no way to enforce them.
This is why it is a good idea to learn how to identify spammy email headers. Spammy email headers tend to come from similar IP addresses. One way to learn which IP addresses are bad is to use a reverse email search. This will help you to learn not only who the person who is sending the spam email is, but where they´re from and what their IP address is.
You can then use the information you´ve garnered from your reverse email search to put the sender on your "blocked senders" list. This will help you to avoid their emails in order to keep your computer (and your identity) as safe as you possibly can.

