xMatters SMS Reference Guide


At xMatters, we realize that our customers use our services to handle critical notifications, and understand the concerns that customers have with SMS carriers and providers. We know that every carrier and country handles SMS messages differently, and we strive to implement the best SMS solution for our clients based on individual needs, location, and expectations.

This document is intended to provide our customers with guidance and best practices for all SMS-related questions and concerns. While the information within this document is current as of the publication date, it is subject to change.

SMS Alternatives

Due to the unreliable nature of the global SMS delivery network, xMatters strongly recommends that customers leverage SMS in conjunction with another notification channel such as email, voice, or push notifications (the xMatters Mobile App), and not to place sole reliance upon SMS delivery for critical notifications.

The xMatters Mobile App, which implements mobile push notifications, is a preferred alternative to SMS and is available for iOS and Android mobile devices.

SMS Provisioning and Regulation

All xMatters instances are provisioned with SMS by default on both production and non-production environments (if applicable). xMatters maintains partnerships with SMS aggregators to serve as a point of entry into the global network of wireless carriers. These aggregators manage network connections and peer directly with wireless carriers or with other aggregators to provide global coverage.

SMS networks and wireless providers do not follow common standards.  Some countries set regulatory guidelines to which all in-country wireless carriers adhere, these standards can vary widely in their scope and complexity.  Other countries may choose to not regulate SMS messaging, this can result in each wireless carrier setting independent standards of service.

Person to Person (P2P) vs Application to Person (A2P) SMS 

Wireless carriers can distinguish between a person sending an SMS message versus an application sending an SMS message. A2P SMS messages generally fall under stricter scrutiny as there is high potential for abuse.  In most cases this doesn't impact xMatters as we provision high volume numbers. This difference is important if customers test SMS delivery by using P2P message from a phone, the results of such a test may not reflect true SMS delivery success.

A Changing Regulatory Landscape

Over the past several years, countries have changed how they regulate SMS volume. This is mostly due to the recognition that SMS is susceptible to fraudulent activity and a desire to allow individual citizens to control their privacy. Countries often require organizations to register numbers and provide examples of messages with volume estimates. We're also seeing a trend for regulators to request proof of in-country business registration and tax documentation. In extreme cases, commercial SMS is blocked entirely.

Often these regulations are applied without prior notice, meaning SMS delivery suddenly stops working or becomes inconsistent. When these cases are brought to our attention, xMatters works to resolve with our aggregators but, depending on the country and their requirements, it may take weeks to months to fully resolve.

Short Codes and SMS Volumes

Certain countries require a “short code” to handle SMS volumes in excess of 10,000 per month. For each of these countries, xMatters has obtained the necessary short code, which will allow customers to immediately take advantage of high-volume notification scenarios. Volumes are based on counts of single SMS messages within the character limit of 160 characters. xMatters messages in excess of 160 characters may be ‘split’ into separate messages and counted as multiple messages when determining volume.

It is critical to note that SMS regulations within individual countries are continually evolving, and country-specific short code requirements can change. It is strongly recommended that customers undertake sizing and planning exercises to identify necessary SMS volumes and countries for delivery, to help understand any risk areas.

For a complete list of the currently supported countries, and the rate per message, see the following links:

Lead Times

xMatters is constantly reviewing SMS delivery options and proactively addressing regulation changes wherever possible. In the event of sudden changes to SMS delivery in a country, we'll work with our providers to determine the available options. Based on the SMS aggregator and wireless carrier processes, this process could take a significant amount of time (weeks to months). Countries where the SMS aggregator does not have existing data-sharing relationships may require additional provisioning time.

In-Country and Out-of-Country SMS Delivery 

Depending on country configuration, some messages will be delivered from in-country Sender IDs. This means that the originating phone number of the SMS will be within the same country as the recipient. For a list of SMS Sender IDs and related information please see:

SMS Numbers Used by xMatters

In many cases, SMS numbers are provisioned out-of-country. This means that the originating phone number of the SMS will be from a different country than the recipient; for example, an SMS to a recipient in Portugal may originate from a UK (+44) phone number.

These provisioning methods ensure that xMatters has maximum global coverage. Clients should be aware of these configurations in the context of their specific user base.

As regulations intended to combat spam and fraud evolve, we have seen an increasing trend of limitations to out-of-country SMS usage. Often these changes happen without notice and can impact SMS delivery or responses.

Blocking International SMS

xMatters has encountered an increase of cases where specific end users have blocked international SMS messages, and users with settings or mobile contracts that allow incoming international SMS but restrict outbound. These scenarios may restrict end users from receiving or responding to xMatters SMS notifications.

Unsolicited SMS Filtering

Much like email providers attempt to filter spam, some wireless carriers attempt to identify and filter unsolicited messages from their networks. This is for two specific reasons:

  • To reduce the load on the overall wireless infrastructure.
  • To limit fraud and spam activity. 

Specific spam identification algorithms vary across wireless carriers and are kept strictly confidential. Nevertheless, xMatters has identified some situations when wireless carriers are likely to filter SMS messages as spam:

  • A high volume of the same message sent to a large number of users simultaneously over a short period of time.
  • A change to baseline message volume to specific numbers.
  • Low outbound-to-inbound response ratio.

Wireless carriers believe that users will not generally reply to spam SMS. The higher percentage of inbound SMS responses, the less likely it is that outbound messages will be classified as spam. As a result, a common xMatters use case that could potentially trigger SMS carrier spam filters is sending a series of FYI (one-way) notifications to large groups.

Country or Region Specific SMS Considerations

Government regulations are constantly changing and can be applied differently in countries across the world. These regulations and changes often have a significant impact on the ability to deliver SMS reliably on a global basis.

United States

The United States has begun introducing 10 DLC (10 Digit Long Code) regulations. This regulation is specific to organizations wanting to use SMS for Marketing and Sales by leveraging a 10-digit number.  xMatters does not fall into this regulation category as we do not send marketing or sales notifications.


Canada restricts marketing content and requires Transactional messages to be delivered via a short code.

For more information on Canada's Anti Spam Legislation (CASL) see https://fightspam-combattrelepourriel.ised-isde.canada.ca/site/canada-anti-spam-legislation/en


India has stringent regulations regarding the delivery of all SMS. Messages are categorized into one of two categories: transaction and promotional.

  • Transactional messages are used to communicate informational messages. Generally, the recipients of these messages have an existing relationship with the sender and expect the message based on a prior action.  xMatters messages are categorized as Transactional
  • Promotional messages are highly restricted and limited to marketing and sales activity.

For more information please see https://www.trai.gov.in/


As each country in Europe regulates SMS numbers and policies individually, there can be significant differences between each country.  All countries in the EU adhere to GDPR practices which pertain to the end user's control over their own privacy by requiring a method for individuals to opt in or opt out of SMS messages.

Regulations are geared toward marketing-related SMS, often requiring an explicit opt-in to receive messages. If an end-user has chosen to opt-out of receiving SMS messages, it could impact their ability to receive xMatters notifications as well.

SMS Message Length

Due to the nature of the protocol, a native SMS message is considered to be fewer than or equal to 160 characters (including spaces). Longer SMS messages are split into 160 character segments, each sent independently. xMatters supports long SMS messaging (with some limitations as detailed in this article), but neither xMatters nor the SMS aggregators control the reassembly of the messages as this is a function of the mobile device.

Longer SMS messages are susceptible to reassembly errors, missing segments, and segments delivered in a manner that cannot be reassembled. Longer messages are also more prone to delays, truncation, or delivery failure.

Customers should evaluate the benefits and drawbacks of allowing more than 160 characters in SMS notifications. Enabling long SMS could result in inconsistent results across message recipients, specifically if the messages are targeted to recipients in multiple countries. Limiting SMS messages to fewer than 160 characters will ensure consistent behavior for all message recipients, across all carriers and devices.

Use of Special Characters

SMS was developed on a subset of the standard Unicode character set.  This standard, commonly known as SMS Default Characters defines the characters that will fall within a 160-character segment.

SMS Default Characters:

@ £ $ ¥ è é ù ì ò Ç Ø ø Å å Δ _ Φ Γ Λ Ω Π Ψ Σ Θ Ξ ^ { } \ [ ~ ] | € Æ æ ß É ! " # % & ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ? A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Ä Ö Ñ Ü § ¿ a b c d e f g h I j k l m n o p q r s t u v x y z ä ö ñ ü à [Space] [Line Feed] [Return]

The use of other characters outside of the default set will reduce segment length limits to 70 characters or less and potentially introduce other failure points as not all telecom providers support special characters.

Glossary of Terms

  • SMS (Short Message Service) - A common form of text messaging used across multiple devices. SMS messages are limited to 160-character segments (including spaces).
  • Segment - An extension to SMS that allows sending of longer messages by breaking the message into 160-character chunks. Segments are received by the handset and reassembled into a longer message.
  • Mobile Carrier - An independent service provider that offers mobile telephone services.
  • Aggregator - A service provider that offers connection to several mobile carriers or other aggregators.  xMatters uses aggregators to access SMS networks.
  • Sender ID - The number that appears on the handset as the calling party.
  • Handset - Commonly a mobile phone or device that can receive SMS messages.
  • Short Code - A short number typically registered to a business or entity sending high volume SMS.
  • Long Code - A "typical" length telephone number able to send SMS messages.
  • Unicode - An international standard that defines how letters, numbers, and symbols in different languages are represented in computer systems and software.
  • SMS Default Characters - A subset of Unicode that defines characters commonly used in SMS messages. Using characters outside of this subset reduces segment length to 70 characters.
  • In-Country SMS - A Sender ID that orginates within a local area.
  • Out-of-Country SMS - A Sender ID that originates from an international number.
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