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A2P Messaging Use Case Best Practices

Lexicon of core concepts and notions

All messaging traffic is required to comply with relevant laws and regulations, including (but not limited to) the Telephone Consumer Protection Act (TCPA). Please note, this article does not constitute legal advice. Please also refer to SignalWires Messaging Requirements and Code of Conduct as well. The following list includes best practices and guidelines for different A2P messaging use cases.

A2P vs P2P

Messages are considered A2P by default

Being that SignalWire is an API platform, all messages that leave the platform are automatically classified as A2P by the downstream carriers (even if you are really sending P2P traffic). That said, if you have an actual P2P use case, you would need to apply for an exemption with the carriers. Getting approved for a P2P exemption would eliminate any carrier related Network Access Fees related to A2P traffic. You can contact your sales representative to help you get started with that process.


The consumer must give appropriate consent

Make sure users explicitly say they want messages from you.

The single most important practice is ensuring you have accurate, reliable consumer opt-in specific to the type of messages you are sending consumers. Generally, opt-out rates are consistently low when you have obtained reliable and clear consumer opt-in consent. At anytime, SignalWire or wireless carriers may require evidence from you (or your customers) of documented opt-in consent for a particular message.

Single Number Use

Utilize single number for identity

Don’t spread your campaigns over several numbers.

Using a single number for both text and voice calls is not only a best practice, it’s also a better overall user experience. Avoid spreading messages across many source phone numbers, specifically to dilute reputation metrics and evade filters. This is referred to as “snowshoeing” and can result in your content being blocked. If your messaging use case requires the use of multiple numbers to distribute “similar” or “like” content, please discuss with your SignalWire sales representative.

Identify Brand

Identify the brand or business in the body of the message

Your application, service or business name should be included in the content of the body.

For example: “[Your Business Name]: You have an appointment for Tuesday 3:00PM, reply YES to confirm, NO to reschedule. Reply STOP to unsubscribe”

Opt-In Confirmation

Let users know they have been opted in to receive messages from you.

Upon successful opt-in by a mobile subscriber, an opt-in confirmation message will immediately be sent to the mobile subscriber number. Per Cellular Telecommunications and Internet Association (CTIA) guidelines, “A single opt-in confirmation message displaying information verifying your customer’s enrollment in the identified program and describing how to opt out” should be sent.

Example: SignalWire Product Trial Alerts: Welcome to SignalWire Trial Alerts! Msg&data rates may apply. Recurring Messages. Reply HELP for help, STOP to cancel.

SignalWire recommends sending your opt in confirmation message or HELP message (see below) once a month or every 6 messages so customers know how to opt out and how to reach the business if they have questions

Support for STOP

Use of Opt-Out language

Be sure your users can opt out of receiving messages.

The best practice is notifying the consumer of their ability to opt-out from future messages from the message sender. This is especially important when sending informational or promotional messages.

An example would be to include the sentence, “Reply STOP to unsubscribe” to the end of the initial message sent to the consumer, or “reply STOP to cancel”

Processing STOP Keywords

[Only for Toll Free A2P]. Ensuring proper functioning of Opt-Out behavior - STOP keywords

Consumer opt-in and opt-out functionality is enforced at the network level via the STOP and UNSTOP keywords. This functionality cannot be disabled for service providers or message senders.

Message senders have obligations to process the opted-out consumer phone number so it is removed from all distribution lists and be logged as “opted out” from SMS communications. This ensures that future messages are not attempted and consumer consent is honored.

Examples of valid opt-out messages: “STOP” “Stop” “stop” “STop”

For Toll Free SMS, there is no need to send an acknowledgment to the consumer. The opt-out confirmation message returned to a consumer is generic from your network provider and gives instructions on how to opt back into service again with the message sender’s phone number. Below is an example of an opt-out confirmation message sent from your network provider:

NETWORK MSG: You replied with the word "STOP" which blocks all texts sent from this number. Text back "UNSTOP" to receive messages again.

Processing UNSTOP and START Keywords

[Only for Toll Free A2P] Processing Opt-In Keywords specific to Toll Free Texting

Allowing users to opt back in after opting out at the network level.

A consumer can opt back in at any time to receive messages by texting the keyword “UNSTOP” or "START" to a message sender’s phone number. The keyword is not case sensitive and triggers an opt-in only when sent as a single word, with no punctuation or leading spaces (any trailing spaces are trimmed). If the consumer uses the opt-in keyword within a sentence an opt-in is not triggered.

Examples of valid opt-ins: “UNSTOP” “Unstop” “unstop” “UNStop” "START" "Start" "start"

The message returned to a consumer is generic and informs the consumer they can start two-way texting with the message sender’s phone number again.

NETWORK MSG: You have replied UNSTOP and will begin receiving messages again from this number.

Processing HELP Keywords

HELP commands should present a clear way for the end user to identify information about the message sender and how to opt out if necessary. HELP keywords are not required on toll free messages, but strongly suggested. HELP must be managed by the customer - there is no network level processing of HELP.

SignalWire recommends the response to a HELP command includes the following:

  • Business name and description
  • Contact info (TN, TFN or email) for the business
  • Language about any associated fees or charges
  • Instructions on how to opt-out

Example: SW Employee Alerts: Help at 844-567-5048. Msg&data rates may apply. Reply STOP to cancel.

Single Domain

Associate URL - Use a single domain for URLs in your messages

Each campaign should be associated with a single web domain owned by a 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. Below is a list of some examples of common URL shorteners you should avoid:


Additional reading to help you stay compliant

The Cellular Telecommunications and Internet Association (CTIA) is a trade organization that represents the wireless communications industry in the United States. They create and maintain lots of great resources to help understand the complex telecom environment.

To learn more about industry guidelines, check out CTIA Best Practices.

You can also check out the CTIA Short Code Monitoring Handbook. Though it is about short codes, the same basic principles and rules apply.