How to Avoid SMS Filtering
  • 04 Mar 2024
  • 4 Minutes to read
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How to Avoid SMS Filtering

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Article Summary

TLDR on carrier filtering

Ignoring carrier regulations can jeopardize SMS campaigns before they even begin. These regulations help protect consumers, so you must consider them when defining your message strategies and drafting your SMS.

The good news is, SMS compliance isn’t too hard. You can easily avoid sounding spammy by:

What is carrier filtering?

Carrier filtering is the action phone carriers like AT&T, Verizon, and T-Mobile take to block the delivery of text messages that are deemed inappropriate or spammy from a specific number or business.

While carrier filtering can be inconvenient for legitimate businesses, it’s essential for the integrity of the SMS industry. If message filtering didn’t exist, spammers and scammers could send as many unwanted messages as they want without consequences.

This would erode consumers’ trust in text messaging, and businesses using SMS marketing responsibly would see a decrease in the channel’s effectiveness.

Why carriers filter text messages

Typically, customer complaints activate messaging filters, with the carrier immediately blocking future messages from the reported number.

But carriers also filter messages to:

  • Ensure SMS marketing compliance with carrier policies, as well as state, local, or country-specific regulations.
  • Enforce SMS marketing rules and regulations and protect their customers from unsolicited or unwanted messages that are abusive, fraudulent, or contain questionable content.
  • Lower the risk of dissatisfied wireless customers taking legal action and seeking damages or moving to a different carrier.

How carrier filtering works

Carriers are super secretive about their message filtering systems to prevent spammers from learning how to dodge these protections, but there are a few methods we do know about.

Unlike email, where the recipient can choose to block email addresses, mobile carriers don’t take user preferences into account when blocking a message. So, you have to be extra careful when sending text messages to customers.

Each wireless carrier has its preferred method of message filtering. Some of these SMS spam filters use a list of keywords that prevent text messages from getting through. Others use advanced machine learning filters that protect customers from unwanted messages in real-time.

6 ways to avoid carrier filtering

Text messages may get blocked for two main reasons: unintentionally spammy content and high-volume texting.

Here are the top ways responsible businesses and organizations can reduce the likelihood of carrier filtering:

1. Don’t use spammy words or special characters 

There’s no official list outlining common spam trigger words/topics, but certain words and phrases are considered spammy and more likely to trigger filtering.

“Financial gain” spam words:

  • Save up to
  • Save big money
  • Billions
  • Money back
  • $$$

“Freebie” spam words:

  • Free $$$
  • Free preview
  • Free access
  • Free trial
  • Free money

“Exaggerated claim” spam words:

  • Risk-free
  • 100% satisfied/free/more
  • Human growth hormone
  • You will not believe your eyes
  • Cure baldness

“Fear of Missing Out (FOMO)” spam words:

  • This won’t last
  • You have been selected
  • Take action
  • Limited time
  • Don’t delete

General-use SMS spam words:

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

The risk of carrier filtering increases when texts contain special characters (like % and #), emojis (😭), and words in all caps.

2. Keep texts short

Whenever possible, keep your text messages short and sweet, not long and rambling.

While you can send text messages up to 1,600 characters, there are few (if any) times when a text message would warrant using that many characters. One to three sentences are typically sufficient.

To avoid getting their messages flagged as spam when sharing links:

  • Use a branded shortened link. Don’t forget, if you use a popular unbranded URL shortener, such as, you can expect to be automatically blocked, as these services are often used by spammers to disguise suspicious links. 
  • Never end messages with a link. Here's an example of a way to include links in your messages: “Jane, you can edit your profile here [link to page]. We look forward to staying in touch with you.”
  • Don’t send naked links. A naked link is a link that does not include “https://” before the link. The best practice is to always send links that begin with https://.

4. Personalize your content

Generic and repetitive messages that are sent to hundreds or thousands of people at once tend to get caught up in SMS filters.

While registering your numbers with carriers reduces the risk of this causing filtering, you want to ensure that your messaging is offering consistent value and is not repetitive. This can be done using features like merge fields to personalize their text messages and sound less robotic.

5. Get explicit permission to text your contacts

Before sending a single text, you need to receive written consent (also called an opt-in) from your recipients.

Even if you’ve already collected a client’s information for another purpose, like sending order updates, you should still ensure that the recipient wants to receive messages via text.

Not only does this help keep your messages from being blocked, but it’s required by the Telephone Consumer Protection Act (TCPA), which protects people from automated and unwanted messages.

6. Follow the CAN-SPAM rules

The CAN-SPAM Act is one of the more well known SMS marketing laws. It regulates how you can send text messages and to whom.

This act gives recipients the right to opt out of business communications with a specific business and sets penalties if the business doesn’t respect their request.

Here are some of the CAN-SPAM regulations:

  • Be upfront about what you’re selling and asking from your clients.
  • Mention the company you represent.
  • Follow SMS opt-in best practices and let recipients unsubscribe from your texts whenever they want to.

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