Area Mail is NTT Docomo's emergency alert service. It broadcasts earthquake early warnings, tsunami alerts, special weather warnings, and municipal evacuation notices to all Docomo devices in the affected area. au and SoftBank offer equivalent services, collectively called "emergency alerts."
Area Mail uses CBS (Cell Broadcast Service) technology. Unlike 1-to-1 SMS, CBS simultaneously broadcasts from base stations to all devices in the target area. This ensures delivery even during disaster-related network congestion. Reception is free.
Area Mail forces alert sounds even in manner mode, displaying messages on screen. This design ensures life-critical information reaches users. However, it cannot reach devices in airplane mode, out of range, or powered off.
The 2011 Great East Japan Earthquake highlighted Area Mail's importance. MVNO devices now support it, though some overseas SIM-free phones may not. Verify "Emergency Alerts" is enabled in settings. See disaster phone guide for more.