US and Canada Carrier Filtering


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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 Fix Your Funnel 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, Fix Your Funnel automatically slows the send rate of batched messages.

Carriers in the U.S. and Canada usually report to Fix Your Funnel 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.

As of this writing, Verizon is the only carrier in the U.S. and Canada that has announced a solution for this. However, based on conversations with carriers and network providers Fix Your Funnel expects that other carriers will come out with similar solutions in the future.

FAQ: Message Delivery in the United States & Canada

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

A: No. Fix Your Funnel 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). 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 blacklist after a short period of time. The time period may vary, and carriers do not share this information with Fix Your Funnel (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.