Phone Carrier Text Message Filtering

SMS Carrier Filtering in the United States and Canada

This is a brief overview of text message filtering by wireless carriers in the United States and Canada that can affect the delivery of your EngageCRM text messages. In this guide, you will learn how and why messages are filtered, and options for improving your delivery rates.

Filtering Mechanisms

Carriers in the U.S. and Canada appear to be using adaptive (machine learning) software systems to protect their users. These systems look at both message content and volume and behave very much like email filtering systems. Messages receive a cumulative score based on 1) how many messages have come from a phone number during a certain time period, 2) how many similar messages have transited the carrier’s network, or 3) if the message contains content that makes it a high match for spam (such as sales or promotion type language or links commonly used in other messages identified as spam) or A2P (messages sent via automated and higher volume sending applications). Time periods are measured by the second, minute, hour and day. To assist with this and improve the delivery rate of messages, EngageCRM automatically slows the send rate of batched messages.

Carriers in the U.S. and Canada usually report to EngageCRM when a message has been filtered. If you suddenly see that a large number of your messages are resulting in a status of Undelivered with an error, the carrier’s filtering system has probably recently identified a pattern in your messages that triggered a block.

Carrier Filtering - Recent Developments

As of 2019, carriers’ rules about long code A2P messaging are beginning to change. A major example is Verizon's upcoming 10 digit long code (10DLC) A2P service. This is a service that will specifically allow A2P traffic to be sent using local numbers to Verizon subscribers, with the added cost of a small delivery fee.

Early 2021 AT&T also announced they will be offering higher delivery rates for businesses, along with an increase in fees per message for those who have had their business and messaging campaigns approved. As of this writing, T-Mobile (now includes Sprint) has not announced any similar plans. However, based on conversations with carriers and network providers EngageCRM expects that other carriers will come out with similar solutions in the future.

FAQ: Message Delivery in the United States & Canada

Q: What can I do to improve my delivery rate?

A: The main things that you have control over are the content of your messages (use less sales and promotional language), adding opt-out language ("reply stop to unsubscribe"), and the links you are sending. If you are using URL shorteners or link tracking services, you may be lumped in with spammers who also use those same services. To combat this, we allow users to add their own custom domain (or sub-domain) to be used in trackable links sent from campaigns and auto conversations within EngageCRM. This means that usually the only time your messages would be blocked because of your URLs, is if you are identified as sending spam by the carriers. No longer would your links be blocked because of someone else sending spam using the same trackable links as you.

Q: I think my EngageCRM number or message contents may have been blocked by a carrier. Can I get the block removed?

A: In most cases, no. EngageCRM is unable to request any unblocking of phone numbers or message bodies due to filtering unless the messaging in question is true Person-to-Person (P2P) messaging and the block was in error (this is VERY uncommon). In cases where MMS messages have been blocked on the Verizon carrier network, we may be able to request that the block be lifted from your sending phone number. Most carrier blocklists in the U.S. and Canada for numbers use a “cooling off” period, which means that the numbers will automatically be removed from the blocklist after a short period of time. The time period may vary, and carriers do not share this information with EngageCRM (from observation it is usually up to 24 hours). If the content of your text messages does not also change, carriers’ content filtering systems will likely continue to block your messages.

Q: Can I get my messages whitelisted or pre-approved by carriers?

A: No. U.S. and Canada phone carriers do not whitelist messages from 10 digit long code numbers.