Skip to main content

Why Carrier Filtering Matters for SMS Marketing — and How to Avoid It

Consumers check their text messages more than 11 times a day—more than any other app. That’s why SMS marketing is such a powerful tool for businesses. You can reach individual customers, groups, or your entire contact list with a message that’s almost guaranteed to be seen.

But there’s a catch: if you’re not careful, your well-meaning message could be flagged as spam and blocked by wireless carriers.

Fortunately, it’s easy for legitimate businesses to avoid this. By understanding how carrier filtering works, knowing what content raises red flags, and following a few best practices, you can significantly reduce your risk of being filtered.

What Is Carrier Filtering?

Carrier filtering is the process mobile carriers like AT&T, Verizon, and T-Mobile use to block text messages that appear spammy, misleading, or inappropriate. If your message gets flagged, it won’t be delivered—hurting your campaign and your brand’s credibility.

While it can be frustrating for honest businesses, filtering is essential to protect consumers and preserve the integrity of SMS as a communication channel. Without it, spammers would flood users with unwanted texts, and SMS marketing as a whole would become less effective.

Why Carriers Block Messages

Message filtering typically kicks in when customers report a message, but there are several other reasons a message might be blocked:

  • To comply with carrier and legal requirements

  • To protect customers from fraudulent, abusive, or unsolicited content

  • To avoid customer complaints that could lead to legal actions or customer churn

  • To enforce the appropriate use of messaging streams (A2P vs P2P)

How Carrier Filtering Works

Carriers don’t reveal exactly how their filtering systems operate, but here’s what we know:

  • Each carrier uses its own combination of spam filters, keywords, and algorithms.

  • Unlike email, text message filtering does not take recipient preferences into account.

  • Filters can block texts based on message volume, content, formatting, or even URLs.

  • Some filters rely on keyword lists; others use machine learning to spot suspicious behavior in real time.

6 Ways to Help Avoid Getting Filtered

Text messages may be blocked due to spam-like content or high sending volume. Here’s how responsible businesses steer clear of filters:

1. Comply with CAN-SPAM Regulations

The CAN-SPAM Act sets clear rules for marketing messages, including:

  • Being honest about your offer and who you are

  • Including your business name clearly

  • Allowing recipients to unsubscribe easily

Failure to comply can result in penalties and blocked messages.

2. Obtain Clear Permission (Opt-In)

Always get explicit consent before sending promotional texts. Even if a customer gave their number for order updates, that doesn’t mean they’ve opted in for marketing messages.

The Telephone Consumer Protection Act (TCPA) requires written consent for promotional SMS. Not following this rule can lead to fines—and increased filtering risk.

3. Avoid Spammy Words and Characters

There’s no official list, but certain terms frequently trigger filters. Avoid phrases related to:

Money/Exaggerated Claims:

  • “Save big money,” “Billions,” “$$$”

  • “Risk-free,” “100% free,” “Money back”

  • "100% satisfied"
  • "You will not believe your eyes"

Freebies:

  • “Free trial,” “Free access,” “Free $$$”

Fear of Missing Out (FOMO) Tactics:

  • "Limited time", “Don’t delete", "You’ve been selected", "This won’t last"

General-use SMS spam words:

  • Important information regarding
  • Information you requested
  • Requires initial investment
  • Social security number
  • Check or money order

Also avoid:

  • Special characters like %, #, or emojis 😭

  • ALL CAPS messaging

4. Keep Messages Concise

Less is more in SMS marketing. While you can send up to 1,600 characters with MMS, most effective messages are only 1–3 sentences. Long texts feel spammy and increase filtering risk.

  • Use branded or custom short links—not public shorteners like bit.ly

  • Don’t place a link at the end of your message

  • Always include “https://” to avoid suspicion

Example:
✅ “Lisa, our Labor Day sale is live! [link] Shop now for the best prices.”
🚫 “Click here: bit.ly/xyz123”

6. Personalize Your Messages

Generic blasts to large lists often trigger spam filters. Use segmentation and personalization tools to:

  • Address customers by name

  • Tailor messages based on preferences or purchase history

  • Offer real value in every message

If it doesn’t feel like a real person wrote it, it’s more likely to get flagged.

Final Thoughts: Stay Compliant, Stay Deliverable

Carrier filtering is designed to protect users and ensure SMS remains a trusted communication channel. But it can block your campaigns if you ignore the rules.

The good news? Staying compliant isn’t hard:

✅ Personalize your content
✅ Avoid spam triggers
✅ Follow legal and industry guidelines
✅ Get proper opt-ins and honor opt-outs
✅ Send messages at a reasonable pace

For even more peace of mind, use an SMS platform that stays current with best practices and helps ensure your messages get delivered.

No Comments
Back to top