Phone number marked SPAM ou SPAM POTENTIEL

Cellular phone providers use systems such as Nomorobo to identify unwanted calls. These systems evaluate calls based on a scoring scale. When calls exceed a certain threshold, they are marked as SPAM, and it is the providers themselves who decide at what threshold calls will be labeled this way.

It is important to note that these evaluations are primarily based on the caller ID and are not related to STIR/SHAKEN protocols. Sometimes, a call may be marked as SPAM on a mobile phone because the STIR/SHAKEN signature token did not reach the cellular provider, which is mainly due to the complexity of the public switched telephone network (PSTN).

The solution is to register your caller ID (your company’s phone number) with the Free Caller Registry or First Orion (for U.S. numbers) or HIYA (for Canadian numbers). It is always preferable to do this proactively before your phone number is marked as SPAM or POTENTIAL SPAM.

NOTE: STIR/SHAKEN standards are a set of procedures designed to verify the identity of callers. These standards help combat unwanted calls received by the public.

April 2026: Some US carriers have recently begun filtering inbound and outbound calls using AI-based filters instead of the aforementioned lists. They respond with a SIP 603+ code that includes the reason for the block and a URL to request a remedy. Here are the URLs found so far:
T-Mobile: https://callreporting.t-mobile.com/
Verizon: https://voicespamfeedback.com/