SMS FAQ

This article answers commonly asked questions about the SMS service.

Sending and receiving messages

How can I receive messages using Azure Communication Services?

Azure Communication Services customers can use Azure Event Grid to receive incoming messages. Follow this quickstart to set up your event-grid to receive messages.

Can I receive messages from any country or region on toll-free numbers?

Toll-free numbers aren't capable of sending or receiving messages to or from countries or regions outside of the United States (US), Canada (CA), and Puerto Rico (PR).

Can I receive messages from any country or region on short codes?

Short codes are domestic numbers and aren't capable of sending or receiving messages to/from outside of the country or region it was registered for. For example: US short code can only send and receive messages to and from US recipients.

How are messages sent to landline numbers treated?

In the United States, Azure Communication Services doesn't check for landline numbers and attempts to send it to carriers for delivery. Customers are charged for messages sent to landline numbers.

Can I send messages to multiple recipients?

Yes, you can make one request with multiple recipients. Follow this quickstart to send messages to multiple recipients.

I received an HTTP Status 202 from the Send SMS API but the SMS didn't reach my phone, what do I do now?

The 202 returned by the service means that the message you queued to be sent wasn't delivered. Use this Quickstart: Handle SMS events to subscribe to delivery report events and troubleshoot. Once the events are configured, inspect the deliveryStatus field of your delivery report to verify delivery success or failure.

How to send shortened URLs in messages?

Shortened URLs are a good way to keep messages short and readable. However, US carriers prohibit the use of free publicly available URL shortener services. This is because the ‘free-public’ URL shorteners are used by bad-actors to evade detection and get their SPAM messages passed through text messaging platforms. When sending messages in the US, we encourage using custom URL shorteners to create URLs with dedicated domain that belongs to your brand. Many US carriers block SMS traffic if they contain publicly available URL shorteners.

To increase the chances of your messages being delivered, the following list shows examples of common URL shorteners you should avoid:

• bit.ly
• goo.gl
• tinyurl.com
• Tiny.cc
• lc.chat
• is.gd
• soo.gd
• s2r.co
• Clicky.me
• budurl.com
• bc.vc

Opt-out handling

How does Azure Communication Services handle opt-outs for toll-free numbers?

Opt-outs for US toll-free numbers are mandated and enforced by US carriers and cannot be overridden.

• STOP - If a text message recipient wishes to opt out, they can send STOP to the toll-free number. The carrier sends the following default response for STOP: "NETWORK MSG: You replied with the word STOP, which blocks all texts sent from this number. Text back UNSTOP to receive messages again."
• START/UNSTOP - If the recipient wishes to resubscribe to text messages from a toll-free number, they can send START or UNSTOP to the toll-free number. The carrier sends the following default response for START/UNSTOP: “NETWORK MSG: You have replied UNSTOP and will begin receiving messages again from this number.”
• Azure Communication Services detects STOP messages and blocks all further messages to the recipient. The delivery report indicates a failed delivery with status message as “Sender blocked for given recipient.”
• The STOP, UNSTOP, and START messages are relayed back to you. Azure Communication Services encourages you to monitor and implement these opt-outs to ensure that no further message send attempts are made to recipients who opt out of your communications.

How does Azure Communication Services handle opt-outs for short codes?

Azure communication service offers an opt-out management service for short codes that allows customers to configure responses to mandatory keywords STOP/START/HELP. Before provisioning your short code, you're asked for your preference to manage opt-outs. If you opt-in, the opt-out management service automatically uses your responses in the program brief for Opt in/ Opt out/ Help keywords in response to STOP/START/HELP keyword.

How does Azure Communication Services handle opt-outs for short codes in United States?

Azure communication service offers an opt-out management service for short codes in US that allows customers to configure responses to mandatory keywords STOP/START/HELP. Before you provision your short code, you're asked for your preference to manage opt-outs. If you opt in, the opt-out management service automatically uses your responses in the program brief for Opt in/ Opt out/ Help keywords in response to STOP/START/HELP keyword.

Example:

• STOP - If a text message recipient wishes to opt out, they can send STOP to the short code. Azure Communication Services sends your configured response for STOP: "Contoso Alerts: You opted out and will not receive any more messages."
• START - If the recipient wishes to resubscribe to text messages from a short code, they can send START to the short code. Azure Communication Service sends your configured response for START: “Contoso Promo Alerts: 3 msgs/week. Message & Data Rates May Apply. Reply HELP for help. Reply STOP to opt-out.”
• HELP - If the recipient wishes to get help with your service, they can send HELP to the short code. Azure Communication Service sends the response you configured in the program brief for HELP: "Thanks for texting Contoso! Call 1-800-800-8000 for support."

Azure Communication Services detects STOP messages and blocks all further messages to the recipient. The delivery report indicates a failed delivery with status message as “Sender blocked for given recipient.” The STOP, UNSTOP, and START messages are relayed back to you. We encourage you to monitor and implement these opt-outs to ensure that no further message send attempts are made to recipients who opt out of your communications.

How does Azure Communication Services handle opt outs for alphanumeric sender ID?

Alphanumeric sender ID cannot receive inbound messages or STOP messages. Azure Communication Services does not enforce or manage opt-out lists for alphanumeric sender ID. You must provide customers with instructions to opt out using other channels such as, calling support, providing an opt-out link in the message, or emailing support. For more information, see messaging policy guidelines.

How does Azure Communication Services handle opt outs for short codes in Canada and United Kingdom?

Azure Communication Services doesn't control or implement opt-out mechanisms for short codes within Canada and the United Kingdom. Recipients of text messages have the option to text ‘STOP’ to unsubscribe or ‘START’ to subscribe to the short code. These requests are relayed as incoming messages to your event grid. It is your responsibility to act on these messages by resubscribing recipients or ceasing message delivery accordingly.

Short codes

What is the eligibility to apply for a short code?

Short Code availability is restricted to paid Azure subscriptions that have a billing address in the United States. Short Codes can't be acquired on trial accounts or using Azure free credits. For more information, see the subscription eligibility page.

Can you text to a toll-free number from a short code?

Azure Communication Services toll-free numbers are enabled to receive messages from short codes. However, short codes aren't typically enabled to send messages to toll-free numbers. If your messages from short codes to Azure Communication Services toll-free numbers are failing, check with your short code provider if the short code is enabled to send messages to toll-free numbers.

How should a short code be formatted?

Short codes don't fall under E.164 formatting guidelines and do not have a country code, or a plus sign (+) prefix. In the SMS API request, your short code should be passed as the five (5) to six (6) digit number you see in your short codes page without any prefix.

How long does it take to get a short code? What happens after a short code program brief application is submitted?

Once you submit the short code program brief application in the Azure portal, the service desk works with the aggregators to get your application approved by each wireless carrier. This process generally takes eight (8) to twelve (12) weeks. All updates and the status changes for your applications are communicated via the email you provide in the application. For more questions about your submitted application, email acstnrequest@microsoft.com.

Alphanumeric sender ID

Important

Effective June 30, 2024, unregistered alphanumeric sender IDs sending messages to UK phone numbers will have its traffic blocked. To prevent this from happening, a registration application needs to be submitted and be in approved status.

How should an alphanumeric sender ID be formatted?

Formatting guidelines:

• Must contain at least one letter
• Upto 11 characters
• Characters can include:
  • Upper case letters: A - Z
  • Lower case letters: a - z
  • Numbers: 0 - 9
  • Spaces

Is a number purchase required to use alphanumeric sender ID?

Using an alphanumeric sender ID doesn't require you to purchase any phone number. You can enable alphanumeric sender ID through the Azure portal. See enable alphanumeric sender ID quickstart for instructions.

Can I send SMS immediately after enabling alphanumeric sender ID?

We recommend waiting for 10 minutes before you start sending messages for best results.

Why is my alphanumeric sender ID getting replaced by a number?

Alphanumeric sender ID replacement with a number may occur when a certain wireless carrier doesn't support alphanumeric sender ID. This is done to ensure high delivery rate.

Toll-Free Verification

Important

Effective January 31, 2024, only fully verified toll-free numbers will be able to send traffic. Unverified toll-free numbers sending messages to US and CA phone numbers will have its traffic blocked.

What is toll free verification?

The toll-free verification process ensures that your services running on toll-free numbers (TFNs) comply with carrier policies and industry best practices. This also provides relevant service information to the downstream carriers, reduces the likelihood of false positive filtering and wrongful spam blocks.

This verification is required for best SMS delivery experience.

What happens if I don't verify my toll-free numbers?

SMS to US phone numbers

Effective January 31, 2024, the industry’s toll-free aggregator is mandating toll-free verification and will only allow verified numbers to send SMS messages.

New limits are as follows:

Limit type	Verification Status	Current limit	Limit effective January 31, 2024
Daily limit	Unverified	500	Blocked
Weekly limit	Unverified	1,000	Blocked
Monthly Limit	Unverified	2,000	Blocked
Daily limit	Pending Verification	2,000	Blocked
Weekly limit	Pending Verification	6,000	Blocked
Monthly Limit	Pending Verification	10,000	Blocked
Daily limit	Verified	No Limit	No Limit
Weekly limit	Verified	No Limit	No Limit
Monthly Limit	Verified	No Limit	No Limit

Important

Unverified SMS traffic that exceeds the daily limit or is filtered for spam has a 4010 error code returned for both scenarios.

What happens after I submit the toll-free verification form?

After submission of the form, we coordinate with our downstream peer to get the application verified by the toll-free messaging aggregator. While we're reviewing your application, we may reach out to you for more information.

• From Application Submitted to Pending = 1-5 business days
• From Pending to Verdict (Verfied/Rejected/More info needed) = 4-5 weeks. The toll-free aggregator is currently facing a high volume of applications, so new applications can take around eight weeks to be approved.

The whole toll-free verification process takes about 5-6 weeks. These timelines are subject to change depending on the volume of applications to the toll-free messaging aggregator and the quality of your application. The toll-free aggregator is currently facing a high volume of applications due to which applications can take around eight weeks to get approved.

Updates for changes and the status of your applications are communicated via the regulatory blade in Azure portal.

How do I submit a toll-free verification?

To submit a toll-free verification application, navigate to Azure Communication Service resource that your toll-free number is associated with in Azure portal. Navigate to the Phone numbers blade. Select the Toll-Free verification application link displayed as Submit Application in the infobox at the top of the phone numbers blade. Complete the form and submit it.

What is considered a high quality toll-free verification application?

The better the quality of your application, the greater the likelihood of it being approved.

Pointers to ensure you're submitting a high quality application:

• Phone numbers listed are Toll-free numbers
• Complete all required fields
• Your use case isn't listed on our Ineligible Use Case list
• Your opt-in process is documented/detailed
• Your opt-in image URL is provided and publicly accessible
• You follow CTIA guidelines

What are the ineligible use cases for toll-free verification?

High-Risk Financial Services	Get Rich Quick Schemes	Debt Forgiveness	Illegal Substances/Activites	General
Payday loans	Debt consolidation	Work from home programs	Cannabis	Phishing
Short-term, high-interest loans	Debt reduction	Risk investment opportunities	Alcohol	Fraud or scams
Auto loans	Credit repair programs	Debt collection or consolidation	Tobacco or vape	Deceptive marketing
Mortgage loans	Deceptive work from home programs			Pornography
Student loans	Multi-level marketing			Sex-related content
Gambling				Profanity or hate speech
Sweepstakes				Firearms
Stock alerts
Cryptocurrency

How is my data being used?

Toll-free verification (TFV) involves an integration between Microsoft and the Toll-Free messaging aggregator. The toll-free messaging aggregator is the final reviewer and approver of the TFV application. Microsoft must share the TFV application information with the toll-free messaging aggregator for them to confirm that the program details meet the CTIA guidelines and standards set by carriers. By submitting a TFV form, you agree that Microsoft may share the TFV application details as necessary for provisioning the toll-free number.

Character and rate limits

What is the SMS character limit?

The size of a single SMS message is 140 bytes. The character limit per single message being sent depends on the message content and encoding used. Azure Communication Services supports both GSM-7 and UCS-2 encoding.

• GSM-7 - A message containing text characters only is encoded using GSM-7
• UCS-2 - A message containing unicode (emojis, international languages) is encoded using UCS-2

This table shows the maximum number of characters that can be sent per SMS segment to carriers:

Message	Type	Characters used in the message	Encoding	Maximum characters in a single segment
Hello world	Text	GSM Standard	GSM-7	160
你好	Unicode	Unicode	UCS-2	70

Can I send/receive long messages (>2,048 chars)?

Azure Communication Services supports sending and receiving of long messages over SMS. However, some wireless carriers or devices may act differently when receiving long messages. We recommend keeping SMS messages to a length of 320 characters and reducing the use of accents to ensure maximum delivery.

*Limitation of US short code - There is a known limit of ~four (4) segments when sending or receiving a message with Non-ASCII characters. Beyond four segments, the message may not be delivered with the right formatting.

Are there any limits on sending messages?

To ensure that we continue offering the high quality of service consistent with our SLAs, Azure Communication Services applies rate limits (different for each primitive). Developers who call our APIs beyond the limit receive a 429 HTTP Status Code Response.

Rate Limits for SMS:

Operation	Number Type	Scope	Timeframe (s)	Limit (request #)	Message units per minute
Send Message	Toll-Free	Per Number	60	200*	200
Send Message	Short Code	Per Number	60	6000*	6000
Send Message	Alphanumeric Sender ID	Per resource	60	600*	600

*If your company has requirements that exceed the rate-limits, submit a request to Azure Support to enable higher throughput.

Carrier Fees

What are the carrier fees for SMS?

US and CA carriers charge an added fee for SMS messages sent and/or received from toll-free numbers and short codes. The carrier surcharge is calculated based on the destination of the message for sent messages and based on the sender of the message for received messages. Azure Communication Services charges a standard carrier fee per message segment. Carrier fees are subject to change by mobile carriers. For more information, see SMS pricing.

When do we come to know of changes to these surcharges?

As with similar Azure services, customers are notified at least 30 days before the implementation of any price changes. These charges are reflected on our SMS pricing page along with the effective dates.

Emergency support

Can a customer use Azure Communication Services for emergency purposes?

Azure Communication Services does not support text-to-911 functionality in the United States, but it’s possible that you may have an obligation to do so under the rules of the Federal Communications Commission (FCC). You should assess whether the FCC’s text-to-911 rules apply to your service or application. To the extent you're covered by these rules, you are responsible for routing 911 text messages to emergency call centers that request them. You're free to determine your own text-to-911 delivery model, but one approach accepted by the FCC involves automatically launching the native dialer on the user’s mobile device to deliver 911 texts through the underlying mobile carrier.