SMS Spam Filtering & Deliverability in Shape

When you send text messages through Shape, wireless carriers may filter or block a message they believe could be unwanted or non-compliant. Shape also blocks some content before it’s ever sent, so you don’t pay for texts carriers won’t deliver.

This is different from the “Spam Likely” label that can appear on outbound phone calls. Texting doesn’t use the same caller reputation or spam remediation system as calling.

In short:

• Carriers use automated filtering to decide whether each text is delivered
• Shape blocks texts with SHAFT content or words and phrases from prohibited industries before they’re sent
• 10DLC registration helps, but doesn’t guarantee every text is delivered
• Consent, volume, content, links, and list quality all affect deliverability
• An undelivered text doesn’t automatically mean your number has been flagged as spam

How SMS spam filtering works

Wireless carriers use filtering systems, algorithms, machine learning, recipient feedback, and other signals to identify potentially unwanted messaging. These systems may look at:

• The content of the message
• The volume and frequency of messages being sent
• How many similar or identical messages are being sent
• Recipient opt-out activity
• Spam complaints
• Whether recipients previously consented to receive messages
• The reputation and behavior of the sending number
• URLs or domains included in messages
• Whether messaging activity matches the registered 10DLC campaign and use case
• Patterns associated with previously identified spam

Carriers generally don’t publish their exact filtering rules. This is intentional, since public rules would let abusive senders design messages to get around them. As a result, there usually isn’t one specific word, phrase, or action that decides whether a message is filtered. Multiple signals can contribute.

SMS filtering vs. “Spam Likely” calling labels

It’s important to tell SMS filtering apart from spam labels on phone calls.

Calling. When an outbound phone number develops a poor calling reputation, a carrier or caller-ID provider may show labels like Spam, Spam Likely, Scam Likely, or Potential Spam. Shape’s spam remediation service helps identify and address these calling reputation issues.

Texting. Text messages are handled differently. Instead of showing a label, carriers may:

• Deliver the message normally
• Filter the message
• Block the message
• Reject the message
• Return an undelivered status or carrier error

Because of this, Shape’s calling spam remediation doesn’t fix SMS filtering. If you’re having trouble with text delivery, the right next step is reviewing your SMS traffic, registration, messaging practices, and content.

Content Shape blocks before sending

Carriers prohibit certain types of content in business texting. Shape follows 10DLC rules and checks every text before it’s sent, so prohibited content never reaches the carrier.

What does Shape block?

Shape blocks texts that include:

• SHAFT content: content related to sex, hate, alcohol, firearms, and tobacco
• Words and phrases from prohibited industries: content tied to industries and activities carriers don’t allow in business texting

Shape doesn’t publish the exact list of blocked words. Like carrier filtering rules, a public list would make it easier for abusive senders to work around it.

Which texts does this apply to?

All texting in Shape, including:

• Manual texts from a record or the Conversations Center
• Bulk texts
• Drip campaign text steps
• Texts sent by Automated Actions (triggers)
• AI texts

Why does Shape block these texts?

So you don’t pay for texts that won’t deliver. Carriers reject or filter messages with prohibited content. Blocking them up front means you aren’t charged for texts that would never arrive.

To protect your 10DLC registration. Sending prohibited content can lead carriers to audit, restrict, or suspend your 10DLC registration, which can affect every text your company sends. Blocking it keeps your registration in good standing.

What happens when a text is blocked?

The text isn’t sent, and you’ll see this message:

Oops! Prohibited message content detected. Please rewrite your message and try again.

To fix it, review your message for content that falls into one of the categories above, rewrite it, and send it again. If a drip campaign or trigger uses the text, update the template or step so future texts can go out.

What is 10DLC?

10DLC is the registration framework for business texting sent through standard 10-digit phone numbers in the United States. Businesses sending application-based texts are generally required to register information about:

• The business or brand sending the messages
• The intended messaging use case
• How recipients give consent
• Example messages
• Opt-out procedures
• HELP and STOP handling
• Other details about the messaging program

Registration helps carriers understand who’s sending messages and what kind of traffic to expect. 10DLC applies to texts sent to U.S. phone numbers.

However, 10DLC approval doesn’t guarantee every message will be delivered. Carriers can still filter messaging traffic after a campaign is approved. And if your company isn’t registered for 10DLC, carriers can block texts to U.S. numbers even when Shape shows them as sent.

Common reasons texts get filtered

1. High message volume or sudden volume changes

A sudden jump in outbound texts can look unusual to carrier filtering systems. This matters most with bulk texts, large drip campaign steps, automated follow-up, and large batches of similar messages. Keep your texting volume consistent with your normal business activity and registered use case.

2. Sending identical messages at scale

Sending the exact same message to many recipients creates a pattern associated with bulk or automated traffic. It doesn’t automatically mean the message will be blocked, but it can be one of the signals carriers consider. Merge tokens can help personalize each message.

3. High opt-out rates

If many recipients reply STOP shortly after receiving a message, it suggests they weren’t expecting it. High opt-out activity can hurt messaging performance.

4. Recipient spam complaints

People can report unwanted texts as spam through their phone or carrier, and those reports can feed into carrier filtering. Texting people who actually expect and want your messages is one of the most important parts of healthy deliverability.

5. Consent issues

Only text recipients who have given appropriate consent for the messages you’re sending. Consent should match the actual use: someone who shared their number for one purpose doesn’t necessarily expect unrelated recurring marketing texts.

6. Messaging that doesn’t match your registered use case

When you register for 10DLC, you describe the kind of messages you plan to send. Your actual texts should match. For example, a campaign registered for customer service shouldn’t suddenly be used mainly for mass promotions.

7. Message content

Carriers can evaluate the content of each message. Messages that look like unwanted, deceptive, fraudulent, or prohibited messaging may get extra scrutiny. Shape blocks the most clearly prohibited content before it’s sent (see Content Shape blocks before sending above), but carriers can still filter other content.

Don’t try to rewrite messages just to “beat” spam filters. Keep messages clear, legitimate, expected by the recipient, and consistent with your registered use case.

8. Links and URLs

Carriers may check the domains and links in your messages. Whenever possible:

• Use recognizable business domains
• Make sure links are legitimate and working
• Avoid suspicious or misleading URLs
• Avoid unnecessary URL shorteners
• Keep the domain consistent with the organization sending the message

9. Sending to old or low-quality contact lists

Texting large databases of old contacts can cause deliverability problems, especially when recipients no longer recognize your business or don’t remember opting in. Older lists tend to bring more STOP replies, spam complaints, invalid numbers, and unengaged recipients. Before a large campaign to an older list, consider whether those contacts would reasonably expect to hear from you.

STOP and opt-out handling

Recipients must have a clear way to stop receiving messages. Use opt-out language when required, such as “Reply STOP to unsubscribe.”

When a recipient opts out, Shape updates their Text Opt-Out preference so future texts can be blocked. Continuing to text someone after they’ve withdrawn consent can create compliance concerns and hurt your messaging reputation.

What does it mean if a message shows as undelivered?

An undelivered text doesn’t automatically mean your sending number has been flagged as spam. Messages can fail for many reasons, including:

• Carrier filtering
• Invalid or disconnected numbers
• Landline numbers
• Recipient device issues
• Carrier availability
• Messaging restrictions
• 10DLC registration issues
• The recipient blocking your number
• Unsupported or oversized media files in MMS messages, and other carrier-specific errors

Review the delivery status and any carrier error before assuming spam filtering is the cause.

MMS images, videos, and unsupported media

MMS messages can include images and videos. Carriers and messaging providers only accept certain file types, so a file in a format they don’t support can fail to deliver, even when the image or video plays fine on your computer.

Videos exported from Apple software. Videos exported from Apple apps are often saved in Apple’s own version of the MP4 format (M4V). Many messaging providers don’t accept it. Shape automatically converts these videos to the standard MP4 format when it sends them, so you don’t need to re-export anything.

To give your media messages the best chance of delivering:

• Use standard MP4 files for videos
• Use common image formats, like JPG or PNG
• Keep files as small as you can, since large files are more likely to fail
• Send yourself a test before using media in a bulk text or drip campaign

If a media message still doesn’t deliver, try re-exporting the file as a standard MP4 or image, or reach out to Shape Support with the template name and an example of the failed message.

Can Shape remove an SMS spam flag?

There isn’t a texting equivalent of Shape’s calling spam remediation service. Carriers don’t usually filter texts through a visible label, so there’s no “Spam Likely” tag for Shape to remove. Instead, the cause of the deliverability issue needs to be investigated. Depending on the situation, that can include reviewing:

• 10DLC registration
• Message delivery results
• Carrier error responses
• SMS templates and message content
• Sending volume
• Automated campaigns
• Opt-out activity
• Consent practices
• Links in messages
• Recent changes in messaging behavior

What should I do if I think my texts are being filtered?

First, figure out whether the issue is isolated or widespread. A few failed messages are normal and don’t necessarily mean there’s a reputation problem.

If you notice a significant increase in failures, gather a few examples before contacting Shape Support:

• The Shape phone number sending the messages
• Example recipients
• Approximate dates and times of the failed messages
• The SMS template or message content
• Whether the messages were sent manually or automatically
• Whether the issue affects multiple carriers or recipients
• When the issue started

Examples help our team review your messaging activity and delivery information faster.

How to reduce the risk of SMS filtering

The best way to keep strong deliverability is to send legitimate, expected messages rather than trying to work around carrier filters.

1. Only text recipients who have consented to receive your messages.
2. Clearly identify your organization when appropriate.
3. Make opting out easy, and honor opt-out requests.
4. Keep messages consistent with your registered 10DLC use case.
5. Avoid content carriers prohibit, including SHAFT content.
6. Avoid sending unexpected bulk texts to old or unengaged lists.
7. Use legitimate, recognizable links and domains.
8. Watch for unusual jumps in opt-outs or failed messages.
9. Review automated campaigns before sending them to large audiences.
10. Contact Shape Support if you notice a significant or unexpected change in deliverability.

Spam remediation vs. SMS deliverability

When troubleshooting, first figure out whether the problem involves calling or texting.

If your outbound calls show “Spam Likely,” “Potential Spam,” or a similar caller-ID label, that’s a calling reputation issue, and Shape’s spam remediation process may help.

If your texts are failing, being blocked, or appear to be filtered, that’s an SMS deliverability issue. It should be investigated through delivery information, 10DLC registration, messaging behavior, content, consent, and carrier filtering.

Frequently asked questions