Carrier spam filters silently drop non-compliant messages without notifying the sender. Learn the mathematical triggers behind algorithmic spam blocking.
One of the most frustrating aspects of telephony engineering is 'silent delivery drops': an SMS API returns status 200, yet the handset never rings. Modern wireless carriers deploy sophisticated real-time machine learning firewalls to filter unwanted commercial traffic. This guide reveals how these filters operate.
1 The Mechanics of Carrier Spam Firewalls
Carrier firewalls evaluate messages across three primary heuristics:
1. Velocity & Spike Rate: An sudden surge from 5 to 500 messages per minute on a single number triggers temporary quarantine.
2. Content Fingerprinting: Exact matching text sent to dozens of unique numbers without personalization triggers automated bulk-spam flags.
3. Reputation & Complaints: Recipient STOP replies, carrier spam reporting (e.g. forwarding to 7726), and high bounce rates degrade phone number trust.
2 Decoding Error Codes 30007 and 30034
- Error 30007 (Carrier Violation): The carrier's spam firewall flagged the message content as unsolicited or non-compliant.
- Error 30034 (US A2P 10DLC Suspension): The campaign is either unregistered or exceeded its assigned daily throughput ceiling.
Frequently Asked Questions • Carrier Spam Filters & Deliverability
Submit a delivery remediation ticket through your aggregator with full timestamp, sender MSISDN, recipient number, and sample message body evidence.