You will need
  • - private email
  • - Internet connection
First, check in the settings of your e-mail, which records ip addresses from which the user accessed the entrances to your Inbox. On some sites offering electronic mail, you need to activate a special security regime, which will register information about the visits to the mailbox by date, time and IP address.
View information about past inputs in emails and analyze what type of visits do not coincide with those time frames when you personally check your Inbox. Copy the IP address listed in those visits, and then save it in a text file or something record.
Go to the service determination information by IP (you can find it in the Internet for "learn information over ip"). Enter in the field you are interested in IP address and click the "Learn about IP". This service will allow you to learn information about the country, region, city, browser, operating system, and even the network provider the location where it was made the entrance to the mailbox.
You can also compare the IP addresses of those who ever wrote to you on mail with the IP address of the unknown that were included in your mail. To do this, define the place in the code of the letter, where is written the IP of the sender. Identify your IP with the service to determine it. Write any email from your mailbox on the same mailbox, i.e. write themselves.
Open the received e-mail. Now examine the HTML code of the email. In Yandex-mail, for example, you can do this: click on the word "Advanced" and choose "Properties of writing". Find in your code your IP and remember, in what place is this entry.
In the same way, open the HTML-code sent to you by other people letters. Find their IP addresses and compare with the IP address of the unknown visitor of your mail.