How to Remove Quick Email Address Autofill in Gmail
Gmail, a popular Web-based email service provided by Google, has a feature that automatically stores any email address you've sent mail to or received mail from and offers to autofill the "To" field when drafting an email. Even if you don't manually add the contact into your address book, Google suggests these contacts which can be frustrating if you have no desire to email the particular saved address. You can remove addresses that Gmail stores in its autofill database.
Open your Web browser and visit Gmail.com. Input your username and password into the appropriate fields on the right side of the page and click "Sign in" to access your Gmail account.
Click on "Contacts" in the upper left side of the Gmail page. Click "Other Contacts" below the "New contact" button on the left side of the page. A list of all contacts you've emailed or received emails from will appear.
Scroll through the list of email addresses and place a check mark beside specific email addresses to remove those addresses from the Gmail autofill database, or click the check box at the top of the list of addresses to select all email addresses.
Click the "More actions" drop-down button at the top of the list of email addresses, then click "Delete contacts."