SMS Filter

If you have ever felt inundated by an endless barrage of political fundraising texts, retail marketing blasts, and promotional spam, you know how frustrating it is to manually type “STOP” to dozens of unknown numbers every week. In this post, we’ll introduce SMS Filter, a modern, privacy-first Android application designed to automatically detect opt-out requests in incoming messages and reply on your behalf. We’ll explore how the app works under the hood, how you can join our private Google Play testing track to install it today, and how to get the most out of its rich configuration and filtering features.

What is SMS Filter?

SMS Filter is a lightweight background compliance utility for Android that automatically monitors incoming messages for opt-out keywords (such as STOP, END, STOP to quit, or Text STOP to cancel) sent by unrecognized senders. When an automated marketing blast or campaign text reaches your phone, SMS Filter intercepts the message, identifies the required compliance trigger, sends an instant opt-out reply, and notifies you—eliminating the friction of unsubscribing by hand.

Unlike traditional “spam blocker” apps that harvest your contacts or upload your personal message logs to third-party cloud servers, SMS Filter is engineered with a strict zero-data-retention, privacy-first architecture. The application runs entirely on-device and never copies your address book. When an incoming message arrives, the app queries your local Google Contacts and an optional HubSpot CRM integration in real time. If the sender is a recognized family member, friend, or business contact, the message is ignored completely. To protect you against automated SMS ping-pong loops, outgoing replies are shielded by a 24-hour cryptographic cooldown system (storing only salted SHA-256 hashes of sender numbers), while group MMS conversations are automatically protected so the app never broadcasts an accidental “STOP” into family group chats.

How to Get the App via Google Play Internal Testing

Because SMS Filter is currently in active development, it is distributed directly through the Google Play Developer Console Internal Testing Track. This allows early testers to receive direct, secure updates through the Google Play Store with full Google Play Protect verification.

How to Join the Test:

  1. Request Access: Send an email with your Google Play / Gmail account address to bill.roth@gmail.com with the subject “SMS Filter Beta Access”.
  2. Accept the Invite: Once added to the authorized tester list, you will receive an official Google Play opt-in email. Open the link and tap “Accept Invitation”.
  3. Install from Google Play: Tap the link to open the app page directly in the Google Play Store on your phone and tap Install.
  4. Enable Notification Access: Because SMS Filter monitors modern Rich Communication Services (RCS) chat messages and picture MMS messages via Google Messages and Samsung Messages, the setup wizard will prompt you to enable Notification Access for SMS Filter in Android system settings.

How to Use SMS Filter & Feature Tour

Once installed, SMS Filter operates quietly in the background without draining battery. Here is a walkthrough of its key features and how to configure them:

1. The 3-Step Setup Wizard

When you launch the app for the first time, an intuitive onboarding flow guides you through:

  • Welcome & Disclaimer: Clearly explains how auto-replies function and sets user expectations.
  • Granular Permissions: Requests standard telephony permissions (RECEIVE_SMS, SEND_SMS, READ_CONTACTS, and notification posting).
  • Live Connection Test: Runs a real-time diagnostic verifying that local contacts, notification listeners, and optional HubSpot CRM endpoints are operational.

2. Comprehensive Multi-Protocol Ingress (SMS, RCS, and MMS)

Modern Android messaging is no longer just simple cellular SMS. SMS Filter features a multi-protocol ingress architecture that tags every incoming message:

  • [SMS]: Traditional cellular SMS messages reassembled directly from low-level radio broadcast packets.
  • [RCS]: High-resolution Rich Communication Services chat messages intercepted in real time from Google Messages, utilizing RemoteInput pending intents to execute instant in-thread auto-replies.
  • [MMS]: Multimedia texts, image attachments, and long promotional captions resolved through Android’s local telephony MMS store (content://mms/part) so long marketing copy is never truncated.

3. Interactive Activity & Detection Log

The Activity & Detection Log screen provides real-time visibility into every message evaluated by the system:

  • Protocol Badges: Clear visual indicators ([SMS], [RCS], [MMS]) showing how the message arrived.
  • Status Badges: Color-coded status pills indicating whether an opt-out was detected (Reply sent: stop), skipped due to dry-run or 24-hour cooldown (Reply skipped: cooldown), or bypassed for a known contact.
  • Click-to-Message: Originating phone numbers and short codes render as interactive chips at the top of each log card. Tapping any sender chip immediately opens that exact conversation thread inside Google Messages via smsto: intents.

4. Customizable Opt-Out Patterns & Matching Modes

Under Settings ➔ Opt-Out Patterns, you can view and edit the rules the engine uses to recognize opt-out requests. Tap any pattern card to open the interactive Edit Pattern Dialog:

  • Keyword Phrases: Comes pre-seeded with 12 industry-standard compliance phrases (stop, end, stop to cancel, stop to opt-out, stop to quit, stop=end, stop2stop, and end2end).
  • Reply Types: Choose whether the app responds with STOP or END.
  • Matching Modes:
    • ANYWHERE: Matches whenever the keyword appears anywhere within the message body or links (ideal for phrases like stop to opt-out or stop=end).
    • LAST_LINE_EXACT: Matches only when the final non-empty line of the message is exclusively that single word (preventing false alarms on ordinary marketing copy).

5. Custom Stop Lists & Contact Bypass

  • Custom Stop List: Add specific keywords (e.g. brand names, candidate names, or organizations) to ignore messages outright without triggering lookups or replies.
  • Google Contacts & HubSpot CRM Integration: Safely connect a HubSpot Private App token to automatically exempt CRM business leads from auto-replies alongside your personal Google Contacts.

6. Safety & Audio Controls

  • Master Auto-Reply Toggle: Toggle auto-reply off at any time to run the app in “Dry Run / Detection Only” mode.
  • Opt-Out Audio Alerts: Configure a custom notification sound or system beep to notify you whenever an automated unsubscribe has been successfully dispatched.
  • Dual-SIM Smart Routing: Automatically detects which SIM card received the message on dual-SIM devices, ensuring the reply is sent from the matching phone number.

Conclusion

SMS Filter brings sanity back to your mobile inbox by automating one of the most tedious aspects of modern smartphone ownership while maintaining strict privacy boundaries. If you’d like to test the app, drop a line to request internal testing access and take back control of your messaging feed!