Facebook allows users to receive notifications via short message service (SMS), which is the second most popular communication channel after email. Users can choose to receive these notifications about private messages, status updates, comments, tags, or profile changes. There are two types of SMS notifications: "Only about your account" and "Suggested." The former includes Facebook account changes, privacy, login attempts, and password changes, while the latter also includes comments on posts and tags. Activating and configuring Facebook SMS notifications can be done through a user's profile settings, and users can stop receiving these notifications by deactivating their mobile phone from the "Mobile" tab or texting "STOP" to 32665 (FBOOK).