Troubleshooting Deliverability
Understand what makes your messages more likely to be delivered.
The content of your message doesn't match the number you're using
Carriers use filtering systems to detect spam and misuse of numbers. These filtering systems work much like email filtering, where certain content may result in the carrier blocking your message. Content filtering systems will look at both the text of the message itself and the number sending the message.
Automated content such as marketing messages, appointment reminders, chatbots/virtual assistants, notifications, and one-time passwords (OTPs)/PIN codes, is typically identified by carriers as application-to-person (A2P) messaging. In the US and Canada, A2P is restricted by most major carriers to short code (numbers with only 5-6 digits) and toll-free numbers. Verizon has recently allowed A2P messaging on local long code numbers, referred to as 10DLC, although this only applies to Verizon subscribers. Sending automated content over a local long code number will most likely result in your messages being blocked by carriers.
If you're trying to send automated content and are having deliverability issues, make sure your number is approved for A2P.
| Long Code | Toll-Free | |
|---|---|---|
| Messaging Use Case | Application-to-Person (A2P): - Two-factor authentication (2FA) - Account notification - Customer care - Delivery notification - Fraud alert messaging - Higher education - Low volume mixed - Marketing - Mixed - Polling and voting - Public service announcement - Security alert Application-to-Person (A2P), Special: - Agents and franchises - Carrier exemptions - Charity - Emergency - K-12 Education - Political - Proxy - Social - Sweepstake | Application-to-Person (A2P): - Two-factor authentication (2FA) - Account notification - Customer care - Delivery notification - Fraud alert notification - Marketing - Appointment reminders - Chat bots - One-time passwords (OPTs) |
The volume of messages is too great for the number you're using
Carrier filtering systems also monitor the rate at which messages are being sent. Local long code numbers are designed to handle person-to-person messaging, and allow 1 message per second. Exceeding that rate will increase the risk of your messages being blocked. Toll-free numbers are designed to handle business-related messaging and have a slightly greater volume of 3 messages per second allowed.
If you're having delivery issues with sending a large number of messages, consider switching to a higher volume number.
| Long Code | Toll-Free | |
|---|---|---|
| Messages per Second | 1 msg/sec | 3 msg/sec This number can be increased for upgraded accounts. Contact support for more information. |
Your message is too long
Long messages are broken into segments that are sent and then stitched back together for the recipient. This process is called concatenation and most carriers in the US and Canada support it. Although it's not very common, sometimes individual segments can get dropped by the carrier. When messages have more than 10 segments, the chance of a carrier failure goes up. For more details on concatenation, please reference our concatenation guide.
If you try to send a long message and have issues with delivery, try shortening the message. To check how many segments your message will be broken up into, you can use this handy tool.
Your message may have been filtered as spam
Carriers use filtering systems to detect spam and misuse of numbers. These filtering systems work much like email filtering, where certain content may result in the carrier blocking your message. Content filtering systems will look at both the text of the message itself and the number sending the message.
Please review CTIA Best Practices to protect your messages from inadvertently being flagged as spam or nuisance messages.
Updated 6 months ago
