SMS Carrier Filtering in Service Cloud

Why is filtering used?

The following are some of the main reasons for filtering:

1. To comply with the carrier's policies, or with state, local, or country-specific regulations. Compliance can relate to the message’s content or frequency.
2. To enforce rules and regulations that protect mobile subscribers from unwanted or unsolicited messaging, such as SPAM and messages that are abusive, fraudulent, or of questionable content.
3. To prevent P2P messages from being sent through A2P streams, and to prevent A2P messages from using P2P routes. Incorrect routing can affect the line of business (carrier and subscriber) indicated by number type.
4. To reduce the potential for dissatisfied customers who file complaints, take legal action, seek damages, or switch to another carrier for loss of business.

To familiarize yourself with country rules and regulations, refer to SMS Regulations by Country. Because regulations can change, we recommend a legal review of the regulatory bodies that govern the telecommunications systems in the country or territory where you plan to do business.

How are messages filtered?

Filtering techniques can vary from one carrier and country to the next. Filters can be triggered any number of ways, such as from a defined list of terms or from advanced logic with the use of adaptive software systems and machine learning.

Carriers can look at content or volume and, through algorithms, use a scoring system that triggers filtering or blocking when a threshold is met. Scoring can be based on a particular time period, message similarity, message frequency, or when content is deemed as possible SPAM or A2P, such as when content contains a URL.

Machine learning helps these systems adapt constantly as different messages pass through them. As a result, it can be difficult to determine why or how a message was filtered. Upon request, some carriers provide information verifying that a message was blocked, while others don’t. Some carriers simply report messages as undelivered to protect the analysis and replication of their filtering algorithms.

Filtering techniques and practices are proprietary and kept strictly confidential by carriers to ensure that they can’t be reverse-engineered or circumvented. Just as spammers continuously adapt their approach, carriers continuously change their heuristics to protect subscribers from spammers.

What are some best practices to protect against filtering?

Learn the rules and regulations of your target market. And consider periodically validating your use case, phone numbers, and content for any changes that could impact message delivery. Also, you can apply the following best practices no matter the regulatory logic for a particular market.

1. Provide clear and easy opt-out instructions. Message recipients can reach out to their carriers for many reasons. For instance, perhaps a recipient believes that they were contacted in error, that it wasn’t clear how to opt out, or that their privacy wasn’t respected. In any of these cases, they can request that the carrier block messages.
2. Avoid URLs. If you intend to include a link, relevancy and frequency are important. Particularly problematic are shortened URLs, which have a high potential for getting marked as SPAM. If you plan to include a link, they should be associated with a single web domain owned by the customer. Although a full domain is preferred, a URL shortener may be used to deliver custom links. You should avoid common, public, or shared domain shorteners. For example: Bit.ly, Goo.gl, Tinyurl.com, Tiny.cc, Lc.chat, Is.gd, Soo.gd, S2r.co, Clicky.me, budurl.com, Bc.vc.
3. Personalize the content. Using identical messages from the same name is a sure way to get flagged and blocked by filtering algorithms. Identical messages don’t indicate typical P2P behavior.
4. Limit the amount and ratio of messaging for P2P. A significant number of messages within a short period of time from the same number isn’t typical human behavior. If there’s an expectation of larger-than-normal personalized messages, using multiple numbers can mitigate the risk.
5. Understand the messaging hours of operation of the target audience. Guidelines for allowable business messaging can vary from country to country. If you’re unclear, limit messaging to the expected hours of operation of your target audience, and consider their time zone.
6. Keep messaging professional and clearly identify the sender. By identifying the business, you remind the recipient who you are and that they gave you consent to message them.

What if my messages were incorrectly blocked or filtered?

Messages blocked by filtering result in the associated number being added to the carrier’s blocked list. The number is only removed after the carrier’s defined (automated) period of time. Carrier’s don’t unblock the number unless it’s clearly blocked in error, which is difficult to validate due to the proprietary nature of filtering.

Long codes blocked for legitimate reasons aren’t eligible for, and Salesforce can’t request, unblocking or adding the number(s) to the allowed list.

Short codes are pre-registered with the local carrier for use case approval, which results in pre-approved allowed listing. But this allowed listing is limited to a particular type of pre-approved traffic.

Verify that messages aren't blocked by each of the major carriers.

To confirm filtering, test against all major carriers. We know of instances where one carrier blocks an SMS message, but another provider received the message. For example, in the US, test with AT&T, Verizon, and T-Mobile/Sprint to verify that messages are received on the mobile device.