Two-Step Verification: Disabled by default for all new accounts, enabling this option adds an additional layer of security to senders accounts through an SMS Authentication Code* and sender Challenge Questions in effort to prevent against unauthorized account access.
Once enabled, users attempting to change passwords or modify certain security settings will be required to provide an Authentication Code sent via. SMS to the mobile phone on record and answer a series of Challenge Questions prior to modifying these settings.
*Please Note: Two-Step Verification requires a mobile phone with the ability to receive SMS (text) messages, standard messaging rates may apply.
See Also: User Guide: Two-Step Verification