There are a few ways to find all of the email addresses associated with a particular computer. You can look for the email addresses that are used on your computer, or you can look for the email addresses that, for whatever reason, have been saved onto your computer.
Email Addresses Used on a Computer
Find email addresses that have been used on a computer for a program such as Outlook or another computer-based email program.
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Go to Tools and click "Accounts."
Read through the list of email addresses associated with various accounts in that email program.
Repeat with other computer-based email accounts.
Find email addresses that have been used on your computer with web-based email programs, such as Gmail or Hotmail. First go to the login page for that email service.
Click on the box where users would input their email address to log in. Click the down arrow on your computer keypad. Sometimes browsers, such as Mozilla, will give you a list of email addresses that have been input into that field.
If your browser doesn't accept this command, or someone was using a different browser, or cleared the cache or cookies after use, there is no way to tell which web-based email addresses were checked from your computer.
Email Addresses Stored on a Computer
Find the email addresses that are stored on your computer, whether in saved contact lists, documents, or files, by going to the Start menu and clicking "Find."
Input the @ sign into the field and click "Search."
Wait several hours for the search of your hard drive to be complete.
Go through the documents and files that show up. This will include any file, at any time, where the @ sign was used. You can pick through these files and find saved email addresses.