Alphanumeric Sender ID the SMS fails to send

Question

Alphanumeric Sender ID the SMS fails to send

stewart sayers 0

I have been Approved for a Alphanumeric Sender ID which is HomeHeatHub but when using this Alphanumeric Sender ID the SMS fails to send. I'm using the Connector Azure Communication Services SMS in SharePoint list Power Automate.

I read something about the number not been "white listed", but if this is the case, how do we overcome this?

Code view of the Power Automate:

{
  "type": "OpenApiConnection",
  "inputs": {
"parameters": {
  "body/from": "HomeHeatHub",
  "body/smsRecipients": [
    {
      "to": "+44798********"
    }
  ],
  "body/message": "Test from Stew",
  "body/smsSendOptions/enableDeliveryReport": true,
  "body/smsSendOptions/tag": "TestSMS"
},
"host": {
  "apiId": "/providers/Microsoft.PowerApps/apis/shared_azurecommunicationservicessms",
  "connection": "shared_azurecommunicationservicessms",
  "operationId": "SendSMSv2"
}
  },
  "runAfter": {}
}

Details below of the example failed to send SMS:

TenantId: "I have removed this for this Q&A"

MessageId: 14ea1439-cfc8-4736-b914-ea14c8cf3667

TimeGenerated: 04/08/2026, 11:17:54.390

OperationName: SMSDeliveryReportsReceived

CorrelationId: SMSDeliveryReportsReceived

ResultType: SMSDeliveryReportsReceived

ResultDescription: SMSDeliveryReportsReceived

DurationMs: 397

PhoneNumber: HomeHeatHub

NumberType: PreRegisteredAlphaSenderId

Country: GB

Failed: ErrorCode: 5000. ErrorMessage: Message failed to deliver, Please reach out Microsoft support team for more details

Abhinaba Das 105 Reputation points Microsoft External Staff Moderator

2026-08-22T20:10:17.5433333+00:00
Hi @stewart sayers

Thank you for providing the delivery report details.

Since the sender ID is shown as PreRegisteredAlphaSenderId and the destination country is GB, the sender ID appears to be recognized as a pre-registered UK alphanumeric sender. Also, your Power Automate action has successfully submitted the message to ACS, as the failure is being returned later through the SMS delivery report.

The reported ErrorCode 5000 – “Message failed to deliver, Please reach out Microsoft support team for more details” indicates a delivery failure that requires further investigation. This does not appear to be something that can be resolved by “whitelisting” the recipient phone number in Azure Communication Services.

Could you please confirm the following over message:

Is HomeHeatHub still showing as Approved under the Preregistered Alphanumeric Sender ID section in the same ACS resource?

Does the issue occur for multiple UK recipient numbers, or only for this specific number?

Are all failed messages showing the same ErrorCode 5000?

Could you also confirm whether you can successfully send an SMS to the same recipient using another supported sender type, such as a UK mobile number?

For UK SMS, traffic from unregistered alphanumeric sender IDs is blocked; however, in your case the telemetry already identifies the sender as PreRegisteredAlphaSenderId, so verifying the current approval status and whether the issue affects multiple recipients will help narrow this down.

Reference:

https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/sms/enable-alphanumeric-sender-id

https://learn.microsoft.com/en-us/azure/communication-services/concepts/sms/concepts

https://learn.microsoft.com/en-us/azure/communication-services/concepts/sms/sms-faq

Kindly let us know if the above helps or if you need further assistance on this issue.

Please upvote if the information was helpful—this helps others in the community as well.

1 answer

Your answer

Answer 1

For Azure Communication Services, URL whitelisting is not managed by Azure. URL filtering is performed by telecom carriers, so an approved pre-registered alphanumeric sender ID does not mean URLs are whitelisted, and there is no Azure portal, API, or verification method to confirm whether a URL has been accepted by the carrier.

In this case, the failure is not resolved by adding a whitelist entry in Azure Communication Services. Carrier-side filtering can block delivery based on the URL itself, redirects, tracking parameters, unregistered domains, or message format.

For sending with an alphanumeric sender ID, Azure Communication Services supports using an alphanumeric sender ID as the from value, and sending is done through CLI, API, or SDK rather than relying on portal-only behavior. The documented sender formats for SMS include:

E.164 phone number
short code
alphanumeric sender ID such as CONTOSO

Practical next steps:

Keep the from value as the approved sender ID: HomeHeatHub.
Enable delivery reporting, which is already configured in the flow, and review delivery details to confirm whether the carrier is rejecting the message.
If the failing messages include URLs, test with:
- no URL
- the plain root domain only
- no redirects or tracking parameters
If messages without links succeed but messages with links fail, that points to carrier-side URL filtering rather than an ACS configuration issue.
If the issue persists even for simple text-only messages, open a Microsoft support request with the message ID and delivery report details, because the documented Q&A guidance for delivery failures that are not explained by URL filtering is to involve support.

The Power Automate payload shown is consistent with using an alphanumeric sender ID as the sender value.

References: