The easiest way is to enter the address of the mailbox in a search engine. If the person when-that for some reason register on any website, leave your e-mail on forums, writing messages, you will find it. The user could for many years as to forget that he was once given advice to go to a fortune teller, or was in the group of "How to lose weight in 5 days", or sold the wooden planks... And the Internet has not forgotten, preserved. Good for you.
Use the programs for instant messaging such as Mail Agent, ICQ or any other, where it is possible to search contacts by name on the mailbox. For this, of course, such a program, and it is better to all you need to install on your computer, run and turn to look for with them the right address.
For example, you need to check your mailbox In the window of your agent, find the "Add contact" and enter the desired e-mail in the search line. In a second there will be information, most likely, with their name, gender and even the age of the person. What else says about him, can be found by clicking "Profile". Also the data from a social network "My World". Many people in the World write about a lot of information: marital status, education, place of birth and residence, Hobbies, etc. you will Also see friends of friends, interests (the groups to which the user belonged).