> ## Documentation Index
> Fetch the complete documentation index at: https://www.cometchat.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> How CometChat sends unread-message SMS fallbacks, what to configure, and where to go next.

SMS is the fast fallback when push/email are missed: if a message stays unread beyond your wait window, CometChat can send a concise text that brings users back to the conversation.

## How it works

* **Trigger**: Fires when a chat message remains unread past the wait window you set.
* **Templates**: Keep payloads lightweight (sender, short snippet, optional deep link) in Templates & Sounds.
* **Preferences/DND**: Honors per-user/per-conversation mutes, global DND, and quiet hours before sending.
* **Providers**: Connect Twilio or a custom provider in the dashboard; CometChat handles fan-out.
* **Recipients**: Store verified phone numbers via API and respect opt-in/opt-out for your region.
* **Observability**: Use logs to confirm sends and diagnose delivery issues.

## Key capabilities

* Unread-based SMS nudges for 1:1 and group chats.
* Template variables for sender and a short preview; optional deep links to reopen the chat.
* Quiet hours, mutes, and DND enforcement to prevent spam.
* Plays well with push/email as layered fallbacks.

## Setup checklist

1. Connect your SMS provider (Twilio or custom) in the dashboard.
2. Configure SMS templates and privacy in [Templates & Sounds](/notifications/templates-and-sounds); keep bodies concise and compliant.
3. Set wait windows, per-day caps, and overrides in [SMS Preferences](/notifications/sms-preferences); keep bodies concise and compliant.
4. Ensure user phone numbers are stored/verified via API; honor opt-out rules.
5. Test unread triggers and monitor delivery in [Logs](/notifications/logs).