Pre-registered Alphanumeric Sender ID and URL:s

Fredrik Molntuss 20 Reputation points
2025-12-19T09:29:54.2966667+00:00

We filed for an order and were approved some months ago.Sending SMS without a link works fine. Sending a link with our company address works fine. But the actual URL:s we asked to be whitelisted is not working and all fail to deliver.

Is there any additional steps that needs to be taken to verify domains? We can't find any clear ways to file a request to whitelist (new) URL:s or find a way to verify which domains are actually whitelisted.

We tried to reach out to Phone Number Service, but they refer back to the ACS team for deliverability issues.

But this largely seem like an issue with the registration of the alphanumeric sender ID. All I would like to know is what additional steps can be taken and where to turn next.

Azure Communication Services
Answer accepted by question author
Golla Venkata Pavani 7,440 Reputation points Microsoft External Staff Moderator
2025-12-19T10:24:52.21+00:00

Hii @Fredrik Molntuss ,

Thank you for contacting us about the issue with SMS delivery when using your pre‑registered alphanumeric sender ID and specific URLs.

For Azure Communication Services (ACS), the behavior you are seeing is expected in certain cases. While your sender ID has been successfully pre‑registered and approved, it is important to note that URL filtering is performed entirely by telecom carriers, not by Microsoft or ACS.

Because of this, sender ID approval does not include URL whitelisting, and Azure does not provide a portal, API, or verification method to validate whether a URL has been accepted by the carrier. Carriers maintain their own filtering rules and may block URLs that include redirects, tracking parameters, unregistered domains, or formats that do not match the version they previously approved.

Microsoft documentation also confirms that inconsistent delivery, such as SMS without links working, or messages with a simple company URL succeeding while others fail, typically indicates carrier-side filtering, not an ACS configuration problem.

Please let us know in comment section below if you have any further queries.

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/troubleshooting-info?tabs=csharp%2Cjavascript%2Cdotnet
https://learn.microsoft.com/en-us/azure/communication-services/concepts/sms/concepts

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