When sending SMS messages through Shape, wireless carriers may occasionally filter or block a message they believe could be unwanted or non-compliant.
This is different from the “Spam Likely” label that can appear on outbound phone calls. SMS does not use the same caller reputation or spam remediation system as voice calling.
Instead, carriers use automated filtering systems to evaluate messaging traffic and determine whether individual messages should be delivered.
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 evaluate factors such as:
- 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 associated with 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 or unwanted traffic
Carriers generally do not publish their exact filtering algorithms. This is intentional because making those rules public could allow abusive senders to design messages specifically to bypass them.
As a result, there usually isn’t one specific word, phrase, or action that determines whether a message will be filtered. Multiple signals can contribute to the carrier’s decision.
SMS Filtering vs. “Spam Likely” Calling Labels
It’s important to distinguish SMS filtering from spam labels associated with phone calls.
Calling
When an outbound phone number develops a poor calling reputation, a carrier or caller-ID provider may display labels such as:
- Spam
- Spam Likely
- Scam Likely
- Potential Spam
Shape’s spam remediation service is designed to help identify and address these types of calling reputation issues.
SMS
Text messages are handled differently.
Rather than displaying a “Spam Likely” caller-ID 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 process does not remediate SMS filtering.
If you’re experiencing issues with text message delivery, the appropriate troubleshooting process is to review your SMS traffic, registration, messaging practices, and deliverability.
What Is 10DLC?
10DLC is the registration framework used for business messaging sent through standard 10-digit phone numbers in the United States.
Businesses sending application-based messaging are generally required to register information about:
- The business or brand sending the messages
- The intended messaging use case
- How recipients provide consent
- Example messages
- Opt-out procedures
- HELP and STOP handling
- Other information about the messaging program
Registration helps carriers understand who is sending messages and what type of traffic they should expect.
However, 10DLC approval does not guarantee that every message will be delivered.
Carriers can still filter messaging traffic after a campaign has been approved.
Common Reasons SMS Messages May Be Filtered
1. High Message Volume or Sudden Volume Changes
A sudden increase in outbound messaging can look unusual to carrier filtering systems.
This can be particularly relevant when sending:
- Bulk SMS campaigns
- Large drip campaign steps
- Automated follow-up
- Large batches of similar messages
Messaging volume should be consistent with the organization’s normal business activity and registered messaging use case.
2. Sending Identical Messages at Scale
Sending the exact same message to a large number of recipients can create a messaging pattern associated with bulk or automated traffic.
This does not automatically mean the message will be blocked, but message similarity can be one of the signals considered by carrier filtering systems.
3. High Opt-Out Rates
If a large percentage of recipients respond with STOP or otherwise opt out shortly after receiving messages, that can indicate that recipients were not expecting the communication.
High opt-out activity can negatively affect messaging performance.
4. Recipient Spam Complaints
Consumers can report unwanted text messages as spam through their phone or wireless carrier.
Those reports may contribute to carrier filtering and reputation systems.
For this reason, messaging people who actually expect and want the communication is one of the most important factors in maintaining healthy SMS deliverability.
5. Consent Issues
Businesses should only send messages to recipients who have provided appropriate consent for the messaging being sent.
The messaging ecosystem places significant emphasis on consumer consent and the ability to revoke that consent.
Consent should also correspond with the actual messaging use case. Someone providing their phone number for one purpose does not necessarily mean they expect unrelated recurring marketing messages.
6. Messaging That Does Not Match the Registered 10DLC Use Case
When registering a 10DLC campaign, the business provides information about the type of messages it intends to send.
Actual messaging traffic should reasonably correspond with that registered use case.
For example, a campaign registered around customer service communication should not suddenly be used primarily for unrelated mass promotional messaging.
7. Message Content
Carrier filtering systems can evaluate the actual content of messages.
Messages may receive additional scrutiny when they contain patterns commonly associated with unwanted, deceptive, fraudulent, or prohibited messaging.
Avoid attempting to rewrite messages specifically to “beat” carrier spam filters. Messaging should instead be clear, legitimate, expected by the recipient, and consistent with the registered use case.
8. Links and URLs
Links can also affect deliverability.
Carriers and messaging providers may evaluate domains and URLs contained within messages as part of their filtering process.
Whenever possible:
- Use recognizable business domains
- Make sure links are legitimate and functional
- Avoid suspicious or misleading URLs
- Avoid unnecessary URL shortening
- Keep the domain consistent with the organization communicating with the recipient
9. Sending to Old or Low-Quality Contact Lists
Messaging large databases of old contacts can create deliverability problems, particularly when recipients no longer recognize the business or do not remember opting in.
Older lists may generate higher rates of:
- STOP responses
- Spam complaints
- Invalid numbers
- Unengaged recipients
Before launching a large SMS campaign to an older database, consider whether those contacts would reasonably expect to receive the message.
STOP and Opt-Out Handling
Recipients must have a clear way to stop receiving messages.
Messages should use appropriate opt-out language when required, such as:
“Reply STOP to unsubscribe.”
When a recipient opts out, that preference should be respected.
Continuing to send messages after someone has withdrawn consent can create compliance concerns and contribute to poor messaging reputation.
What Does It Mean if a Message Shows as Undelivered?
An undelivered SMS does not automatically mean the sending number has been identified as spam.
Messages can fail for many reasons, including:
- Carrier filtering
- Invalid or disconnected numbers
- Landline numbers
- Recipient device issues
- Carrier availability
- Messaging restrictions
- Registration issues
- Recipient blocking
- Other carrier-specific errors
The delivery status and available carrier error information should be reviewed before assuming spam filtering is responsible.
Can Shape Remove an SMS Spam Flag?
There isn’t a direct SMS equivalent of Shape’s calling spam remediation service.
If a carrier is filtering SMS traffic, Shape cannot simply remove a “Spam Likely” label from the number because SMS filtering does not generally work through that type of visible label.
Instead, the underlying cause of the deliverability issue needs to be investigated.
Depending on the situation, this may include reviewing:
- 10DLC registration
- Message delivery results
- Carrier error responses
- SMS templates
- Sending volume
- Automated campaigns
- Opt-out activity
- Consent practices
- URLs contained in messages
- Recent changes in messaging behavior
What Should I Do if I Think My Shape Text Messages Are Being Filtered?
If you’re seeing an unusual number of undelivered messages, first determine whether the issue appears isolated or widespread.
A few failed messages are normal and do not necessarily indicate a reputation problem.
If you notice a significant increase in failures, gather a few examples before contacting Shape Support.
Helpful information includes:
- The Shape phone number sending the messages
- Example recipients
- Approximate dates and times of the failed messages
- The SMS template or message content being sent
- Whether the messages were manually sent or automated
- Whether the issue affects multiple carriers or recipients
- When the issue first started
Providing examples allows our team to review the messaging activity and available delivery information more efficiently.
How to Reduce the Risk of SMS Filtering
The best way to maintain strong SMS deliverability is to focus on sending legitimate, expected communication rather than trying to work around carrier filtering systems.
As a general rule:
- Only message recipients who have appropriately consented to receive your messages.
- Clearly identify your organization when appropriate.
- Make opting out easy.
- Honor opt-out requests.
- Keep messaging consistent with your registered 10DLC use case.
- Avoid sending unexpected bulk messages to old or unengaged databases.
- Use legitimate, recognizable links and domains.
- Monitor unusual increases in opt-outs or failed messages.
- Review automated campaigns before sending them to large audiences.
- Contact Shape Support if you notice a significant or unexpected change in SMS deliverability.
Shape Spam Remediation vs. SMS Deliverability
If you’re troubleshooting a communication issue, the first step is identifying whether the problem involves calling or texting.
If your outbound calls display “Spam Likely,” “Potential Spam,” or a similar caller-ID label:
This is a calling reputation issue and may be appropriate for Shape’s spam remediation process.
If your text messages are failing, being blocked, or appear to be filtered:
This is an SMS deliverability issue and should be investigated through SMS delivery information, 10DLC registration, messaging behavior, content, consent, and carrier filtering.
Keeping these two systems separate helps ensure the issue gets routed to the right troubleshooting process.