Why Text Messages Might Not Be Delivered
Text messages might not be delivered for several reasons:
- The recipient has opted out.
- The mobile number is invalid.
- The carrier blocked the message.
Also see online carrier lookup for phone numbers
Reasons for Message Blockage
Carrier violations occur when carriers (like Verizon or AT&T) believe your message is spam, illegal, or previously blocked by the recipient. Signs of carrier blockage in your logs include:
- Your message content was marked as violating carrier guidelines.
- The phone carrier has blocked this message.
- Sending messages from your user or phone number has been blocked.
Carriers employ sophisticated monitoring systems akin to email spam filters. These systems assign a “cumulative score” to messages, considering factors like the volume of messages sent from a particular number within a specific timeframe and the content of those messages. High cumulative scores can result in future messages being blocked.
Warming Up Your SMS Sending Number
Much like email IP addresses, SMS sending numbers must be gradually introduced to build a solid reputation with carriers and become recognizable to recipients. If you start sending messages from a new number without this process, it can lead to many opt-outs. A high rate of opt-outs can result in your messages being marked as spam.
Types of Sending Numbers
- Short Codes: 5- to 6-digit numbers used for mass texting.
- Toll-Free Numbers: Special 10-digit numbers that start with an 8 (e.g., 800, 888).
- 10-digit Long Codes (10DLC): Standard 10-digit numbers associated with a specific area code.
Best Practices for SMS Marketing
- Monitor Sending Volume: Avoid sending too many identical messages from a single number in a short period. The CTIA suggests staying under 60 messages per minute for long codes.
- Be Careful with URLs: Using URLs, especially public shorteners like “bit.ly,” can trigger filters. Consider using private URL shorteners.
- Encourage Replies: Positive responses from recipients can improve your sending reputation.
- Avoid Flag Words: Words like “gift” with a $ symbol can look like spam. Tailor your content to what your audience expects.
- Identify Yourself: Always let recipients know who you are to avoid being mistaken for spam.
- Handle Opt-Outs Properly: Include “Reply STOP to opt out” in your messages and honor opt-out requests promptly.
What to Do if You Get a Carrier Violation
- Stop Sending to the Blocked Number: Continuing to send messages to a blocked number will reinforce the carrier’s negative assessment.
- Report to Your SMS Marketing Service: If you believe your message should have been delivered, contact your carrier partner.
- Consider Purchasing a Short Code or Registering for 10DLC: Short codes are less likely to face carrier violations. If that’s not an option, register your 10DLC number for higher sending limits.
- Recycle Your Sending Number: As a last resort, get a new sending number and rebuild its reputation.