Originally published at ictdialer.com
If your open-source auto dialer keeps showing up as 'Spam Likely' even on clean, consented calls, the culprit is usually attestation. STIR/SHAKEN signs each call A, B, or C, and calls routed through smaller carriers tend to get B or C. That lower grade drags down your reputation and your answer rate. Here's what the levels mean and how to pull your traffic back up to A.
What STIR/SHAKEN Attestation Levels Mean
STIR/SHAKEN is the framework carriers use to cryptographically sign calls so the receiving network can trust the caller ID. The signing carrier assigns one of three attestation levels:
- A (Full): the carrier knows the customer and confirms they have the right to use the calling number. This is the grade you want.
- B (Partial): the carrier knows the customer but can't confirm the number is theirs.
- C (Gateway): the carrier is just passing the call through and can't vouch for the source at all.
Analytics engines that decide whether to show 'Spam Likely' weigh attestation heavily. A calls sail through. B and C calls get scrutinized, and if your number has any negative signals, they get labeled fast.
The 2026 Attestation Gap Between Big and Small Carriers
Here's the uncomfortable math. In 2026, Tier-1 carriers sign roughly 85% of their traffic, and about 93% of what they sign gets full A-level attestation. Smaller and regional carriers lag badly, with signing rates near 17.5%. So the same consented call that would earn an A on a Tier-1 network often earns a B or C when it originates through a small carrier.
That gap is the whole problem for self-hosted dialer operators. You did everything right on your end, but the originating carrier can't or won't fully attest, and the terminating network treats your call as suspect. Understanding this is the first step, and our primer on what auto dialer software is covers the call-flow basics that make the attestation handoff clearer.
The 2026 Attestation Gap Tier-1 carriers Small carriers 85% signed 93% A-level 17.5% signed mostly B/C Same call, different grade, depending on who originates it. Tier-1 networks sign far more traffic at A-level than smaller carriers do.
Why Open-Source and Self-Hosted Dialers Hit This
When you run your own dialer, you pick your own SIP trunk provider, often a smaller, cheaper wholesaler. That's great for cost and control, but those providers are exactly the ones with low signing rates. Your open-source stack isn't the problem; the origination path is. You're routing legitimate campaigns through a carrier that can't hand you an A.
The trap is assuming better software fixes it. It doesn't. Your dialer can be flawless and still land as 'Spam Likely' if the number and route don't earn full attestation. If you're weighing platforms, our roundup of open source predictive dialers is honest that carrier choice matters as much as the software.
How to Fix the Attestation Gap in 2026
You can close most of the gap with a handful of concrete moves. None of them require abandoning self-hosting:
- Choose an A-level-capable originating carrier. Ask any prospective SIP provider directly what attestation level they assign to your numbers and how they verify ownership. If they can't give you A, keep looking.
- Register your numbers with the RMD. Getting into the industry's registration and reputation systems helps carriers and analytics engines recognize your traffic as legitimate.
- Use branded caller ID and rich call data. Showing your business name and call reason gives recipients a reason to answer and gives analytics engines positive signals.
- Monitor your reputation. Check your numbers across the major analytics platforms regularly and rotate or remediate any that get tagged.
- Keep clean consent records. Documented consent and low complaint rates are what keep your reputation high once attestation gets you in the door.
ICTDialer is auto-dialer and call-center software with predictive, power, and progressive dialing, a WebRTC agent panel, bulk fax, and REST APIs. Those APIs make it straightforward to pull disposition and complaint data into your reputation monitoring so you catch a slipping number before it tanks a campaign. AI-driven reputation scoring is coming soon; for now the monitoring workflow is yours to wire up, and the REST endpoints make that easy.
From Flagged to Delivered B/C attest Spam Likely A-level carrier RMD register branded caller ID A attest trusted rings Three fixes move a flagged call up to A-level and back into the recipient's ringer.
Putting It Into a Campaign
Attestation work pays off only when it feeds your day-to-day dialing. Warm up new numbers gradually, keep dial ratios sane so complaints stay low, and pull your reputation data into your pre-flight checks. If you want a step-by-step frame for running the campaign around these controls, our guide on how to run a predictive dialer campaign lays out the sequence.
Frequently Asked Questions
Why does my legitimate call show as 'Spam Likely'?
Usually because it earned B or C attestation on origination, not because your content is bad. Analytics engines weigh attestation heavily, so a call routed through a small carrier that can't fully attest gets extra scrutiny and often a spam label even when the campaign is fully consented.
Can an open-source dialer earn A-level attestation?
Yes. Attestation is assigned by your originating carrier, not your software. If you route through a SIP provider that verifies number ownership and signs at A, your open-source or self-hosted dialer gets the same grade as any hosted platform.
What is the RMD and why register?
The RMD is the industry registration and reputation infrastructure that helps carriers and analytics engines recognize legitimate callers. Registering your numbers gives your traffic positive standing, which supports better delivery and fewer false spam labels.
Does branded caller ID actually improve answer rates?
It helps in two ways. Recipients are more likely to pick up when they see your verified business name and call reason, and analytics engines read branded, data-rich calls as a positive signal, which supports your overall reputation over time.
How often should I check my number reputation?
Check regularly, at least weekly for active campaigns, across the major analytics platforms. A number can pick up a spam tag quickly, so early detection lets you rotate or remediate it before it drags down a whole campaign's answer rate.
You don't have to give up self-hosting to beat the spam label, you just have to fix the origination path. If you want to see how ICTDialer's dialing modes and REST APIs fit a reputation-first workflow, give it a try and wire your monitoring in.
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