How SMS Filtering Works
Carriers analyze every SMS for spam indicators. Suspicious messages are blocked or delayed without notification to the sender. Filters examine:
- Message content — Keywords, patterns, URLs
- Sender reputation — Historical behavior of the sending number
- Volume patterns — Sudden spikes raise red flags
- Recipient complaints — "Report spam" actions
Common Filter Triggers
Content Triggers
- URL shorteners — bit.ly, tinyurl hide destinations
- Financial terms — "loan", "credit", "debt" without proper registration
- Urgency phrases — "Act now", "Limited time", "Free"
- ALL CAPS — Looks like shouting/spam
- Excessive punctuation — "!!!!!" or "???"
Behavioral Triggers
- Volume spikes — Sudden increase in sending
- High bounce rates — Many invalid numbers
- Complaint rates — Recipients marking as spam
- Unregistered traffic — Missing 10DLC registration
Avoiding Filters
Do
- Complete 10DLC registration
- Use full URLs or branded short links
- Keep messages professional and clear
- Include clear opt-out instructions
- Validate numbers before sending
Don't
- Use generic URL shorteners
- Send to purchased/scraped lists
- Send without consent
- Use ALL CAPS or excessive punctuation
- Spike volume suddenly
Clean your lists. Remove invalid numbers before sending to improve deliverability.
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