We all receive email from an email addresses we do not immediately recognize. Nowadays, so much junk mail and so many phishing scams are going around that you don't want to open an email unless you know who sent it; it might contain a virus or spyware or hold a large file you don't want to download to your computer. There are several ways to identify who an email address belongs to for free.
Check your email address book. This might sound obvious, but nowadays people have hundreds of email addresses. Sometimes we forget an email address that we saved in our address book. So, before going crazy with search parameters, check out your address book.
Read the subject of the email. Sometimes, you can identify an email address owner by looking at the subject line. Many people write their name in the subject line, especially if they are writing from an email address they do not usually use.
Look at the first part of the email address — the part before the @. Many times, part of a first or last name is recognizable. Analyze the first part of the email address and see if you recognize either a first or last name in there. Common email addresses include names with numbers at the end of the email address to make the address unique — you can ignore the number; or a first initial and last name, so take off the first letter and see if you recognize the rest of the email name. Some individuals use a partial last name, especially if the last name is long, or they combine the initials of their first, middle and last names. If you get an email address like "BRF2009@blablablabla.com" try to think if you know anyone whose initials are B.R.F.
Look at the domain name of the email address. Do you recognize it? Does the domain name look similar to a company you know? Domain names are very inexpensive nowadays, so companies and individuals buy them freely. The domain name might belong to a friend of yours who purchased a private domain name, so see if the domain name resembles a first or last name of your friend.
Search for the email address in Google. See if any Web pages come up with that email address.
Search for the domain name in Google. See if there is a website associated with the domain name. See if it is a website for a company that you know or a friends' blog?
View all the headers in the email address. Depending on your email program or software, the method varies, but by viewing all the headers, you can get insight into who the email address belongs to.
Look up the IP address. Do an IP address search to find out where the email originates. See if you recognize the location.
Do a domain name look up search on the domain name of the email address by searching Google for "domain name look up." This returns information on who owns the domain name.
Reverse email search. There are various services online that let you do reverse email searches. Look them up in Google. Some charge money, but some offer at least partial information free or a free limited-time membership.