How Can I Find Out What Email My Twitter Account Is Registered To?by C. Taylor
You can access your Twitter account using its associated email address or your username. The username option enables you to log in to Twitter with the same login details, even after changing your email address. Using this option, you can access your account and locate the email address registered to the account. If you can't find your username to access your account, you'll at least need a list of possible email addresses so you can locate the associated address through trial and error.
Logging Into Twitter
Log in to your Twitter account using your username and password. Your username is the alphanumeric name at the end of your Twitter profile URL. As an example, if your URL was "https://twitter.com/somecoolname," your username is "somecoolname."
Click the "Gear" icon from the top navigation bar and select "Settings."
Click the left "Account" tab and look in the "Email" field for the address registered to your account.
Can't Access Twitter
Visit Twitter's Resent Password page (see Resources).
Enter one of the possible email addresses in the "Enter Your Email Address or Phone Number" field. Do not click "Submit."
Wait a few seconds for a notice to appear at the right of the email field. If you see "Looks Good," the email address is associated with a Twitter account. If you own this email address and you only have one Twitter account, then you have found the registered address. If you see "Email or Phone Is Invalid," then that email address is not linked with a Twitter account; try the next email on your list.