Quick answer: STIR/SHAKEN is the system carriers use to digitally sign phone calls so the network can tell a real caller from a spoofed one. In 2026, calls that are not signed at the highest trust level are increasingly diverted to voicemail or labeled “Potential Spam,” which quietly destroys answer rates for outbound campaigns. If you run an auto dialer, your connect rate now depends as much on call authentication as on dialing speed. The fix is to use numbers you own, get them signed at full attestation through your provider, and keep your consent and opt-out records clean.

You can have the fastest dialer in the world and still watch your campaigns flatline if the calls land as “Spam Likely.” That is the reality of outbound calling in 2026. The phone network now checks a cryptographic signature on every call, and the score that signature carries decides whether the phone even rings the way you expect.

This guide explains how STIR/SHAKEN works, why attestation level is the number that matters, and how to keep an open source auto dialer connecting at a healthy rate.

What STIR/SHAKEN Actually Does

STIR/SHAKEN is a pair of standards that let the originating carrier attach a signed token to a call. That token says, in effect, “I know this customer and I vouch for this number.” The terminating carrier checks the signature and uses it to decide how much to trust the call. There are three attestation levels:

Full attestation (A): the provider knows the customer and confirms they have the right to use the calling number. This is what you want.
Partial attestation (B): the provider knows the customer but cannot confirm the number. Calls often get a weaker pass.
Gateway attestation (C): the provider only knows where the call entered the network. These calls are the most likely to be filtered or labeled.

By 2026, the large carriers sign the overwhelming majority of their traffic, and most of it at A level. Calls that show up with B or C attestation stand out, and carrier analytics treat them with suspicion.

Figure 1: The same call gets a very different reception depending on its attestation level. A level rings clean; B and C invite the spam label.

Why This Hits Auto Dialers Hardest

Outbound campaigns push high volume from a handful of numbers, which is exactly the pattern carrier analytics are tuned to flag. If those numbers are not signed at full attestation, or worse, if they are not numbers you actually own, the system reads the traffic as suspect and starts filtering. Once a number earns a spam reputation, every campaign that uses it suffers, and cleaning that reputation up is slow.

The connect rate is the whole game for a dialer. A campaign that should reach 30% of its list might reach half that if the calls are landing as “Spam Likely.” No pacing trick recovers calls that the recipient’s phone is actively warning them about.

Keeping Your Connect Rate Healthy

ICTDialer is a FreeSWITCH-based auto dialer, and it gives you the controls that keep your traffic on the right side of the filters. The platform handles the dialing; you pair it with carrier and number discipline.

Figure 2: Connect rate is earned. Owned numbers, full attestation, honored opt-outs, and sane rotation build the reputation that gets calls through.

Own and register the numbers you dial from

Use direct inward dial numbers that belong to your account, not borrowed or random caller IDs. Numbers you own can be signed at full attestation, which is the single biggest factor in whether your call rings clean.

Ask your provider about attestation

Not every SIP provider signs at A level for every customer. Before you scale a campaign, confirm what attestation your traffic actually carries. If you are stuck at B or C, that is a conversation to have with your carrier, not a dialer setting.

Keep consent and opt-outs current

A clean list is a quiet list. Recipients who never consented are the ones who report calls as spam, and a flood of spam reports is what tanks a number’s reputation. ICTDialer logs dispositions and opt-outs so a contact who asked to stop does not resurface.

Frequently Asked Questions

Does STIR/SHAKEN apply to open source dialers?

STIR/SHAKEN happens at the carrier level, not inside your dialer software, so it applies to any outbound traffic regardless of the platform. What your software controls is the number discipline, consent handling, and pacing that keep your traffic trustworthy enough to earn full attestation.

Why are my calls showing as “Spam Likely”?

Usually because the numbers are not signed at full attestation, are not registered to you, or have built a poor reputation from spam reports. Fix the attestation and the number ownership first, then give the reputation time to recover.

Can I improve attestation from the dialer side?

Not directly, but you set the conditions for it. Dialing from owned, registered numbers through a provider that signs at A level is how you qualify for the best treatment. The dialer keeps your lists clean so you stay there.

How fast do I have to honor an opt-out?

Current guidance gives businesses ten business days to process a revoked consent, and the contact should never appear in a later campaign. ICTDialer records opt-outs against the contact so the suppression carries forward.

Is ICTDialer built on FreeSWITCH?

Yes. ICTDialer runs on a FreeSWITCH-based engine, which handles the call media and signaling while the platform manages campaigns, pacing, agents, and reporting on top.

Get Started

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STIR/SHAKEN in 2026: Keeping Your Auto Dialer Out of the Spam Folder