Mobile carriers actively scan SMS and MMS messages to protect consumers from spam, fraud, and abusive messaging. Even when a legitimate message is sent successfully, it can get caught up in carrier filtering and be blocked or filtered based on content alone.
If your messages are being blocked, delayed, or inconsistently delivered, this guide will help you identify and fix the most common content-related causes.
How Carrier Content Filtering Works
Carriers evaluate messages using automated systems that look for:
- Spam-like language patterns
- Fraud or phishing indicators
- High-pressure or deceptive phrasing
- Missing opt-out language
- URLs or formatting commonly abused by bad actors
These systems are algorithmic, not human-reviewed, and they adapt constantly. Small wording changes can significantly improve deliverability.
Step 1: Check for Missing or Weak Opt-Out Language
One of the most common reasons messages are filtered.
What to avoid
- No opt-out instructions at all
- Non-standard opt-out language (e.g., “Reply no thanks”)
- Opt-out hidden deep in long messages
What to do instead
Include clear, standard language, such as:
“Reply STOP to opt out.”
To have this opt-out message apply to all campaign texts automatically, simply turn on the opt-out option in your Campaign Settings.
Best practices:
- Include opt-out language in the first message to a consumer
- If messaging is one-way or automated, include it periodically, not just once
- Place it at the end of the message, clearly separated
Step 2: Remove Spam-Triggering Language
Carriers aggressively filter language associated with scams and unsolicited marketing.
High-risk phrases to avoid
- “Free”, “Guaranteed”, “No risk”
- “Act now”, “Urgent”, “Final notice”
- “Limited time offer”
- “You’ve been selected”
- “Winner”, “Congratulations”
- Excessive punctuation (!!!)
- ALL CAPS
Safer alternatives
| Instead of | Try |
| "Act now!" | "Please review when convenient" |
| "Guaranteed approval" | "You may be eligible" |
| "Final notice" | "Following up on your request" |
Tone matters: neutral, informational language performs far better than sales-heavy copy.
Step 3: Use The Correct Company Name
Do not include company names in your messages other than the company you work for.
When registering a 10DLC use case, carriers require you to specify the exact company the messaging traffic is associated with. They actively monitor messages to ensure the number is only used for that registered brand.
If carriers detect references to any other company names, they may block your messages. This includes abbreviations, shortened names, or alternate versions of your company’s name.
Step 4: Avoid Phishing-Like Structures
Even legitimate businesses can accidentally mimic scam patterns.
Red flags for carriers
- Asking for sensitive info (SSN, DOB, passwords)
- Messages that pressure users to click links immediately
- Messages that lack business context
Improve trust signals
- Clearly identify who you are
- Reference why the consumer is receiving the message
- Avoid short, cryptic messages with links
Example (bad):
“Verify your account now: link.co/xyz”
Example (better):
“Hi John, this is ABC Lending following up on your request. You can review details here: example.com. Reply STOP to opt out.”
Step 5: Be Careful With Links
Links are one of the highest-risk elements in SMS.
Common issues
- URL shorteners (bit.ly, tinyurl, etc.) are flagged by the carriers and shouldn't be used.
- Links with random strings or tracking parameters
- Multiple links in a single message
Best practices
- Use your own branded domain
- Keep links readable and minimal
- Limit to one link per message
- Ensure the link destination clearly matches the message context
Step 6: Reduce Repetition and Template Overuse
Sending many messages with nearly identical wording increases the likelihood of filtering.
What triggers filtering
- Same message sent repeatedly to many recipients
- Identical phrasing across campaigns
- No personalization at all
How to improve
- Slightly vary the wording across messages
- Personalize the message using Bonzo merge tags when appropriate (name, context)
- Avoid copy-paste “blast” language
Step 7: Keep Messages Clear, Simple, and Honest
Carriers favor messages that look like legitimate, respectful communication, not advertising blasts.
Best practices
- One clear purpose per message
- Plain language
- No exaggerated claims
- No misleading implications
Good structure:
- Who you are
- Why you’re reaching out
- What action (if any) is needed
- How to opt out
Step 8: Watch for Over-Formatting
Formatting can accidentally trigger spam filters.
Avoid
- Emojis in first contact messages 🚨
- Excessive line breaks
- Symbols like $$$, ###, !!!
- Mixed character sets
Stick to
- Plain text
- Short paragraphs
- Professional formatting
Step 9: Warm Up Your SMS Reputation
When you lease a new number for your SMS marketing, or move from another provider, you need to warm up your sending number reputation to avoid carrier violations.
Warming up your sending reputation is the process of re-introducing the new number to your recipients and establishing a positive reputation with the carriers. This allows your recipients to understand what number you send from and the type of content you send.
Warm up your sending numbers slowly. Remember, new numbers are unknown to recipients and may lead to the prospect opting-out of communicating with you. Too many opt-outs will cause your message to get flagged as a carrier violation. Moreover, when carriers see your text messages for the first time, it’s best to keep your messages simple and concise. Most importantly, don’t use links or any sales language.
Bonzo requires all Members to limit Opt Out rates to below 5%. Opt outs in excess of this can damage your “sending number reputation.”
Note: Warm up your new Bonzo number by communicating with your friends and family. These are people who won’t (or shouldn’t ) opt out of your communication— improving your sending.
Final Checklist Before Sending
Before launching a message, ask:
- ✅ Does this clearly identify my business?
- ✅ Does it explain why the recipient is receiving it?
- ✅ Are you only referencing the name of your company?
- ✅ Is the tone informational rather than promotional?
- ✅ Is opt-out language clear and standard?
- ✅ Are links branded and minimal?
- ✅ Would this message feel trustworthy if I received it?
If you’ve applied the steps in this article and are still seeing a high number of failed messages, please contact Bonzo Support. This may indicate a separate issue, such as a carrier-level block on your phone number.