AWS End User Messaging SMS Best Practices

For the best results for creating and sending messages, we recommend that you perform the following best practices.

SMS and MMS best practices

Additionally, mobile phone carriers continuously audit bulk SMS and MMS senders and throttle or block messages from originators that they determine to be sending unsolicited messages.

Sending unsolicited content is also a violation of the AWS acceptable use policy. The AWS End User Messaging SMS team routinely audits SMS and MMS message, and might throttle or block your ability to send messages if it appears that you're sending unsolicited messages.

In many countries, regions, and jurisdictions, there are severe penalties for sending unsolicited SMS or MMS messages. For example, in the United States, the Telephone Consumer Protection Act (TCPA) states that consumers are entitled to $500–$1,500 in damages (paid by the sender) for each unsolicited message that they receive.

Comply with laws, regulations, and carrier requirements

You can face significant fines and penalties if you violate the laws and regulations of the places where your customers reside. For this reason, it's vital to understand the laws related to SMS and MMS messaging in each country or region where you do business.

The following list includes links to key laws that apply to SMS and MMS communications in some of the major markets around the world. This guide doesn't cover the laws for all locales, so it's important that you research them.

As a sender, these laws can apply to you even if your company or organization isn't based in one of these countries. Some of the laws in this list were originally created to address unsolicited email or telephone calls, but have been interpreted or expanded to apply to SMS and MMS messages as well. Other countries and regions have their own laws related to the transmission of SMS and MMS messages. Consult an attorney in each country or region where your customers are located to obtain legal advice.

Prohibited message content

The following are general prohibited content categories for all message types globally. Some countries might allow content on the list in the following table, but no country actively allows unsolicited content. Some countries or mobile carriers require that you register your number or sender ID with them before live messaging will be enabled. When using or registering a number as an originator, follow these guidelines:

Obtain permission

Never send messages to recipients who haven't explicitly asked to receive the specific types of messages that you plan to send. Don't share opt-in lists, even among organizations within the same company.

If recipients can sign up to receive your messages by using an online form, add systems that prevent automated scripts from subscribing people without their knowledge. You should also limit the number of times a user can submit a phone number in a single session.

When you receive an SMS or MMS opt-in request, send the recipient a message that asks them to confirm that they want to receive messages from you. Don't send that recipient any additional messages until they confirm their subscription. A subscription confirmation message might resemble the following example:

Text YES to join ExampleCorp alerts. 2 msgs/month. Msg & data rates may apply. Reply HELP for help, STOP to cancel.

Maintain records that include the date, time, and source of each opt-in request and confirmation. This might be useful if a carrier or regulatory agency requests it, and can also help you perform routine audits of your customer list.

Opt-in workflow

In some cases, such as US toll-free or short code registration, mobile carriers require you to provide mockups or screenshots of your entire opt-in workflow. The mockups or screenshots must closely resemble the opt-in workflow that your recipients will complete.

Your mockups or screenshots should include all of the following required disclosures to maintain the highest level of compliance.

The following example complies with the mobile carriers’ requirements for a multi-factor authentication use case.

It contains finalized text and images, and it shows the entire opt-in flow, complete with annotations. In the opt-in flow, the customer must take distinct, intentional actions to provide their consent to receive text messages and contains all of the required disclosures.

Other opt-in workflow types

Mobile carriers will also accept opt-in workflows outside of applications and websites, such as verbal or written opt-in if it complies with what has been described in the previous section. A compliant opt-in workflow and verbal or written script will gather explicit consent from the recipient to receive a specific message type. For example, a verbal script that a support agent uses to gather consent before recording into a service database, or a phone number listed on a promotional flyer. To provide a mockup of these opt-in workflow types, you can provide a screenshot of your opt-in script, marketing material, or database where numbers are collected. Mobile carriers might have additional questions around these use cases if an opt-in is not clear or the use case exceed certain volumes.

SMS and MMS specific Terms and Conditions page

Mobile carriers also require that you make a specific set of SMS and MMS Terms and Conditions available to your customers. The following terms and conditions comply with the mobile carriers’ requirements. You can copy these terms and modify them to fit your use case.

Don't send messages to old lists

People change phone numbers often. A phone number that you gathered consent to contact two years ago might belong to somebody else today. Don't use an old list of phone numbers for a new messaging program. If you do, you're likely to have some messages fail because the number is no longer in service, or because some people opted out because they didn't remember giving you their consent in the first place.

Audit your customer lists

If you send recurring SMS or MMS messsages, audit your customer lists on a regular basis. Auditing your customer lists helps to make sure that the only customers who receive your messages are those who are interested in receiving them.

When you audit your list, send each opted-in customer a message that reminds them that they're subscribed, and provides them with information about unsubscribing. A reminder message might resemble the following example:

You're subscribed to ExampleCorp alerts. Msg & data rates may apply. Reply HELP for help, STOP to unsubscribe.

Keep records

Keep records that show when each customer requested to receive SMS and MMS messages from you, and which messages you sent to each customer. Many countries and regions around the world require SMS and MMS senders to maintain these records in a way that can be easily retrieved. Mobile carriers might also request this information from you at any time. The exact information that you must provide varies by country or region. For more information about record-keeping requirements, review the regulations about commercial SMS messaging in each country or region where your customers are located.

Occasionally, a carrier or regulatory agency asks us to provide proof that a customer opted to receive messages from you. In these situations, AWS Support contacts you with a list of the information that the carrier or agency requires. If you can't provide the necessary information, we may pause your ability to send additional SMS and MMS messages.

Make your messages clear, honest, and concise

SMS is a unique medium. The 160-character-per-message limit means that your messages must be concise. Techniques that you might use in other communication channels, such as email, might not apply to the SMS channel, and might even seem dishonest or deceptive when used with SMS messages. If the content in your messages doesn't align with best practices, recipients might ignore your messages. In the worst case scenario, the mobile carriers might identify your messages as spam and block future messages from your phone number.

MMS has a 1,600 character limit for the message body. Your message doesn’t have to be concise, but it should still follow the best practices.

The following section provides some tips and ideas for creating an effective SMS message body.

Identify yourself as the sender

Your recipients should be able to immediately identify that a message is from you. Senders who follow this best practice include an identifying name ("program name") at the beginning of each message.

Don't try to make your message look like a person-to-person message

Some marketers are tempted to add a personal touch to their messages by making their messages appear to come from an individual. However, this technique might make your message seem like a phishing attempt.

Be careful when talking about money

Scammers often prey upon people's desire to save and receive money. Don't make offers seem too good to be true. Don't use the lure of money to deceive people. Don't use currency symbols to indicate money.

Use only the necessary characters

Brands are often inclined to protect their trademarks by including trademark symbols such as ™ or ® in their messages. However, these symbols are not part of the standard set of characters that can be included in a 160-character SMS message. These characters are known as the GSM alphabet. When you send a message that contains one of these characters, your message is automatically sent using a different character encoding system, which supports only 70 characters for each message part. As a result, your message could be broken into several parts. Because you're billed for each message part that you send, it could cost you more than you expect to spend to send the entire message. Additionally, your recipients might receive several sequential messages from you, rather than one single message. For more information about SMS character encoding, see SMS character limits.

Use valid, safe links

If your message includes links, double-check the links to make sure that they work. Test your links on a device outside of your internal network to confirm that links resolve properly. Because of the 160-character limit of SMS messages, very long URLs could be split across multiple messages. You should use redirect domains to provide shortened URLs. However, you shouldn't use free link-shortening services such as tinyurl.com or bitly.com, because carriers tend to filter messages that include links on these domains. However, you can use paid link-shortening services as long as your links point to a domain that is dedicated to the exclusive use of your company or organization.

Limit the number of abbreviations that you use

The 160-character limitation of the SMS channel leads some senders to believe that they need to use abbreviations extensively in their messages. However, the overuse of abbreviations can seem unprofessional to many readers, and could cause some users to report your message as spam. It's completely possible to write a coherent message without using an excessive number of abbreviations.

Respond appropriately

When a recipient replies to your messages, make sure that you respond with useful information. For example, when a customer responds to one of your messages with the keyword "HELP", send them information about the program that they're subscribed to, the number of messages you will send each month, and the ways that they can contact you for more information. A HELP response might resemble the following example:

HELP: ExampleCorp alerts: email help@example.com or call 425-555-0199. 2 msgs/month. Msg & data rates may apply. Reply STOP to cancel.

When a customer replies with the keyword "STOP", let them know that they won't receive any further messages. A STOP response might resemble the following example:

You're unsubscribed from ExampleCorp alerts. No more messages will be sent. Reply HELP, email help@example.com, or call 425-555-0199 for more info.

Adjust your sending based on engagement

Your customers' priorities can change over time. If customers no longer find your messages to be useful, they might opt out of your messages entirely, or even report your messages as unsolicited. For these reasons, it's important that you adjust your sending practices based on customer engagement.

For customers who rarely engage with your messages, you should adjust the frequency of your messages. For example, if you send weekly messages to engaged customers, you could create a separate monthly digest for customers who are less engaged.

Finally, remove customers who are completely unengaged from your customer lists. This step prevents customers from becoming frustrated with your messages. It also saves you money and helps protect your reputation as a sender.

Send at appropriate times

Send messages during normal daytime business hours. If you send messages at dinner time or in the middle of the night, there's a good chance that your customers will unsubscribe from your lists to avoid being disturbed. You might want to avoid sending SMS or MMS messages when your customers can't respond to them immediately.

If you send campaigns or journeys to very large audiences, double-check the throughput rates for your originator phone numbers. Divide the number of recipients by your throughput rate to determine how long it will take to send messages to all of your recipients.

Avoid cross-channel fatigue

In your campaigns, if you use multiple communication channels (such as email, SMS, MMS, and push messages), don't send the same message in every channel. When you send the same message at the same time in more than one channel, your customers will probably perceive your sending behavior to be annoying rather than helpful.

Use dedicated short codes

If you use short codes, maintain a separate short code for each brand and each type of message. For example, if your company has two brands, use a separate short code for each one. Similarly, if you send both transactional and promotional messages, use a separate short code for each type of message or register the short code once for transactional and create another registration for promotional. For more information about requesting short codes, see Request a phone number in AWS End User Messaging SMS.

Verify your destination phone numbers

When you send SMS and MMS messages through AWS End User Messaging SMS, you're billed for each message part that you send. The price you pay per message part varies on the recipient's country or region. For more information about SMS and MMS pricing, see AWS End User Messaging Pricing.

When AWS End User Messaging SMS accepts a request to send an SMS or MMS message, you're charged for sending that message. This statement is true even if the intended recipient doesn't actually receive the message. For example, if the recipient's phone number is no longer in service, or if you sent the message to mobile phone number that wasn't valid, you're still billed for sending the message.

AWS End User Messaging SMS accepts valid requests to send SMS messages and attempts to deliver them. For this reason, you should validate that the phone numbers that you send messages to are valid mobile numbers. You can use the Amazon Pinpoint phone number validation service to determine if a phone number is valid and what type of number it is (such as mobile, landline, or VoIP). For more information, see Validating phone numbers in the Amazon Pinpoint Developer Guide.

Design with redundancy in mind

For mission-critical messaging programs, we recommend that you configure AWS End User Messaging SMS in more than one AWS Region. AWS End User Messaging SMS is available in several AWS Regions. For a complete list of Regions where AWS End User Messaging SMS is available, see the AWS General Reference.

The phone numbers that you use for SMS or MMS messages—including short codes, long codes, toll-free numbers, and 10DLC numbers—can't be replicated across AWS Regions. So to use AWS End User Messaging SMS in multiple Regions, you must request separate phone numbers in each Region where you want to use AWS End User Messaging SMS. For example, if you use a short code to send text messages to recipients in the United States, you must request separate short codes in each AWS Region that you plan to use.

In some countries, you can also use multiple types of phone numbers for added redundancy. For example, in the United States, you can request short codes, 10DLC numbers, and toll-free numbers. Each of these phone number types takes a different route to the recipient. Having multiple phone number types available—either in the same AWS Region or spread across multiple AWS Regions—provides an additional layer of redundancy, which can help improve resiliency.

Handling deactivated phone numbers

A deactivated phone number means that the mobile subscriber has terminated their service or transferred their phone number to a different mobile network provider. Eventually, deactivated numbers are recycled and reassigned to new subscribers. Therefore, it’s possible to mistakenly send an SMS or MMS message to a phone number that now belongs to a different subscriber who has not opted in to your SMS or MMS message program.

Mobile network providers frequently publish deactivation reports that contain a current list of deactivated phone numbers in their networks. These reports are published to help keep your SMS and MMS sending list current and compliant.

Why is handling deactivated phone numbers important?

In the US, the Federal Communications Commission (FCC) considers sending messages to a phone number that belongs to a subscriber who has not opted in to your projects as spam. This stance can result in end-user and mobile network provider complaints, which can then lead to audits, and put your SMS and MMS message sending at risk of being entirely blocked by mobile network providers. In the worst-case scenarios, the FCC can impose fines, or you could be subject to a class-action lawsuit.

Additionally, when you send SMS or MMS messages through AWS End User Messaging SMS, you're billed for each message that you send. By keeping your end-users lists up to date, you can prevent charges on unnecessary messages.

AWS End User Messaging SMS provides a copy of the deactivation reports to allow you to keep all of your end-users lists up to date periodically. These reports originate from mobile network providers and are processed daily. Each report contains a list of phone numbers that have been deactivated on the mobile network provider networks. You should download and compare them to your existing end-users list. Delete all phone numbers from your end-users lists that have been deactivated.

Requesting deactivation reports

Before you can obtain a copy of a deactivation report, you must first request a deactivation report through an Amazon S3 GET OBJECT API request using the REQUESTER PAYS buckets option to download a file. For more information about Requester Pays buckets, see Downloading objects in Requester Pays buckets in the Amazon S3 User Guide.

You pay for requests made against S3 buckets and objects requiring the Requester pays option. S3 request costs are based on the request type, and are charged on the quantity of requests. For more information about S3 request costs, see Amazon S3 pricing.

AWS End User Messaging SMS provides two types of deactivation reports. For ease of use, if you want the most recent deactivation report, you can submit a request using the latest object format. If you want a deactivation report for a specific date, you can submit a request using the date specific object format.

You can use the following template example to request a deactivation report through the AWS CLI. For more information about configuring the AWS CLI, see Configure the AWS CLI in the AWS Command Line Interface User Guide.

Bucket name format: {region}-pinpoint-sms-voice/

Latest object format: /sms-deact-reports/{iso2}/latest-deact-report.csv

Date specific object format: /sms-deact-reports/{iso2}/{YYYY}-{MM}-{DD}-deact-report.csv

In the preceding examples, make the following changes:

The following example shows you how to request the latest deactivation report using AWS CLI command.

aws s3api get-object --bucket us-east-1-pinpoint-sms-voice --key sms-deact-reports/us/latest-deact-report.csv OUTFILE.csv --request-payer requester

The following example shows you how to request a date-specific deactivation report using AWS CLI command.

aws s3api get-object --bucket us-east-1-pinpoint-sms-voice --key sms-deact-reports/US/2023-09-28-deact-report.csv OUTFILE.csv --request-payer requester

After the Amazon S3 GET OBJECT API request is submitted, the deactivation report is downloaded to the OUTFILE.csv specified in the command.

Using the Amazon S3 API, you can get a list of deactivation reports. You can list the deactivation reports only within the embedded sms-deact-reports/us/ folder.

The following example shows you how to get the list of deactivation reports available.

aws s3api list-objects-v2 --bucket us-east-1-pinpoint-sms-voice --prefix "sms-deact-reports/us/" --request-payer requester

Voice best practices

This section contains several best practices related to sending voice messages using AWS End User Messaging SMS. These practices can help with the satisfaction of your recipients, and can protect you from unexpected charges.

Comply with laws and regulations

You can face significant fines and penalties if you violate the laws and regulations of the places where your customers reside. For this reason, it's vital to understand the laws related to automated voice calls in each country where you do business. As a sender, these laws might apply to you even if you don't reside in one of these countries. You are responsible for complying with all applicable laws. Note that some national subdivisions have stricter rules than their parent countries. For example, several US states have rules that are more strict than the US Federal laws concerning voice calls. This information is not intended to be legal advice. Consult an attorney in each country or region where your customers are located to obtain legal advice.

Send at appropriate times

Only send messages during normal daytime business hours in each recipient's time zone. If you send messages at dinner time or in the middle of the night, there's a good chance that your customers will unsubscribe from your lists in order to avoid being disturbed again in the future. Additionally, many countries and regions restrict the days and times at which people can receive automated messages. Although regulations vary by country, it's a good idea to not send messages before 9 AM or after 8 PM. Many countries also prohibit sending messages on Sundays and national holidays. This information is not intended to be legal advice. Consult an attorney in each country or region where your customers are located to obtain legal advice.

Avoid cross-channel fatigue

If you use multiple communication channels (such as voice, email, SMS, and push messages), don't send the same message across multiple channels unless there's a good reason for doing so. If you send the same message at the same time in more than one channel, your customers are likely to perceive this behavior as annoying rather than helpful.

Protect yourself against voice fraud

Because voice calls can be expensive, it's important to secure your AWS account against unauthorized access, and to monitor the destinations of the messages that you send.

 

¹ Prices quoted are accurate as of December 2021. Per-minute rates are subject to change. For current pricing, see AWS End User Messaging Pricing.