Here are the steps to remove an unknown email address from your email account:
Log in to your email account using a web browser or an email client.
Locate the email from the unknown address in your inbox or spam folder.
Open the email and look for the "unsubscribe" or "opt-out" link. Click on the link to unsubscribe from the sender's emails.
If there is no unsubscribe link, you can block the sender by selecting the email and then clicking on the "block" or "spam" button. This will prevent the sender from sending you any more emails.
If the email is not in your inbox or spam folder, it's probably that the email is not coming from your account. In this case, you can try to find the email address on the internet, and look for a way to unsubscribe or report spam.
Alternatively, you can also create a filter or rule in your email client that automatically moves emails from the unknown address to a specific folder or marks them as spam.
Please note that these steps may vary slightly depending on the email service or client you are using. If you have any questions about removing an unknown email address, you can contact your email service provider for support.