Why it matters
SMS filtering directly impacts message deliverability. Carriers and regulatory bodies enforce filtering to protect subscribers and maintain compliant messaging ecosystems. Understanding how filtering works helps you avoid blocks, maintain deliverability, and ensure your SMS traffic follows Whippy’s Messaging Policy and Acceptable Use Policy (AUP).
Key Concepts
SMS filtering: Carrier-driven systems that block or restrict messages considered risky, non-compliant, or spam-like.
Messaging policies: Rules set by Whippy, carriers, and regulators that determine what content and behavior is allowed.
Opt-in compliance: Ensuring recipients have willingly agreed to receive your messages.
Undelivered status: An indicator that the message did not pass carrier filtering or could not be delivered.
Why Message Filtering Systems Exist
Message filtering models serve two main purposes:
Protecting mobile subscribers: Filters block spam, fraud, and abusive content to protect users. Severe violations can result in fines or disconnection by carriers.
Enforcing rules and regulations: Different countries and carriers enforce strict messaging guidelines. Messages that violate these restrictions may be filtered.
How SMS Filtering Works
Filtering varies by region and carrier. Systems range from basic keyword blocks to complex machine-learning models that analyze patterns, frequency, and content types.
Whippy applies filtering aligned with its Messaging Policy and Acceptable Use Policy (AUP) to ensure messages comply with regulatory and carrier requirements.
Preventing Your Messages From Being Flagged as Spam
Reduce the risk of filtering by following these best practices:
Target willing recipients who have clearly opted in, ideally using double opt-in.
Provide clear opt-out instructions when sending campaign messages.
Personalize your messages with details like your name and the recipient’s name.
Avoid sensitive or restricted content such as drugs, alcohol, gambling, or hateful references.
Keep messages concise and avoid emojis, excessive punctuation, or special characters.
Do not resend blocked messages to avoid velocity-based filtering.
Maintain a compliant website with proper terms of service, privacy policy, and opt-in language.
How to Tell If Messages Are Being Filtered
Filtered messages often display an Undelivered status.
However, carriers do not always report filtering transparently, so some filtered messages may appear as “Delivered.”
Why Filtered Messages Are Still Billed
Even when a message is blocked, carriers incur processing costs. Filtered messages are billed to cover these operational expenses and maintain secure messaging systems.
What to Do If Messages Are Being Filtered by Mistake
If you suspect legitimate messages are being filtered:
Collect Conversation IDs showing Undelivered status.
Contact Whippy Support for assistance and escalation to carriers if needed.
Tips and Best Practices
Send only to verified opt-in contacts.
Avoid overly long or repetitive messages.
Monitor delivery performance to catch issues early.
Follow SMS rules for the specific countries you message.
Troubleshooting
Issue | Possible Cause | Fix |
Messages repeatedly undelivered | Content violates policies or resembles spam | Rewrite content and remove high-risk terms |
Filtered messages show as delivered | Carrier misreporting | Evaluate engagement instead of relying solely on delivery status |
Charges applied to filtered messages | Carrier processed message at intake | Review message strategy to reduce filtering |
Filtering appears incorrect | Carrier misclassification | Collect Conversation IDs and contact support |