The best SIP trunk for VICIdial is a carrier that permits dialer traffic in writing, sustains your calls-per-second and channel load without discretionary surcharges, bills short calls in short increments (12/6, not 60/60), signs outbound calls with A-level attestation, and clears short-duration traffic in its terms.
Run any VICIdial SIP provider through the seven criteria below. Every competitor policy, limit and price quoted here links to that provider’s own page, read on 2026-09-24. Terms change, so re-read them before you sign.
We’re a carrier, so we can’t pretend to be neutral — SIPNEX runs VICIdial traffic as its core business, and we score ourselves openly below. The scorecard works whether or not you ever talk to us.
The seven criteria that pick a SIP trunk for VICIdial
| # | Criterion | Pass looks like | Fail looks like |
|---|---|---|---|
| 1 | Dialer tolerance in writing | Terms permit or expressly serve dialer traffic | “Auto-dialing” listed as prohibited use |
| 2 | CPS headroom | Your peak CPS fits without surcharges | Low defaults, discretionary caps |
| 3 | Channel capacity | Channels scale free with usage | Per-channel fees or tiny defaults |
| 4 | Billing increments | 12/6 or similar short increments | 60/60 rounding |
| 5 | Attestation | Carrier signs A-level under its own cert | B/C, or attestation by paperwork only |
| 6 | Short-duration policy | Short calls accepted or clearly priced | Pre-authorization clauses you skipped |
| 7 | US route quality | Low PDD, stable ASR on Tier-1 routes | Grey routes, dead air, spam-flag churn |
1. Dialer-traffic tolerance — in writing
This is the elimination round: a great rate on a trunk that prohibits your traffic is a countdown timer. RingCentral’s Acceptable Use Policy bars RingEX customers from “auto-dialing or ‘predictive dialing.’” Vonage’s Reasonable Use Policy names auto-dialing, telemarketing and operating a call center as impermissible on its residential unlimited plans, and holds unlimited small-business plans to “normal small or home business use.” 8x8’s archived Business Terms (section 15) exclude autodialing, telemarketing and call-center operations from Unlimited PSTN plans and reserve the right to terminate those plans immediately.
Less obvious: Telnyx’s Acceptable Use Policy lists “auto-dialing or predictive-dialing (sometimes referred to as ‘robo-dialing’)” in its general list of improper uses — not only under unlimited plans. Traffic may flow in practice; what counts is what the paper says when a dispute starts. Our survey of SIP providers that allow autodialers goes vendor by vendor.
2. CPS headroom
A predictive dialer’s defining behavior is bursts of simultaneous call attempts. Telnyx’s CPS surcharge article sets a default limit of 20 CPS for each source IP or SIP username, and rejects excess attempts with SIP 503. It adds a monthly Outbound Peak CPS surcharge computed from the 95th percentile of hourly peaks: the first 5 CPS free, then $12 per CPS in the 6–25 band, rising band by band to $30 per CPS above 250. Telnyx’s own worked example prices a 163 CPS peak at $2,448 per month.
Ask every candidate three questions: what’s my default CPS, what does exceeding it cost, and what happens to rejected attempts?
3. Channel capacity vs. per-channel fees
VICIdial hurls calls at whatever concurrency your campaigns demand. Telnyx’s concurrent-call article starts new accounts at 2 concurrent outbound calls, rising to 10 after Level 2 verification, and recommends sharing use-case detail before channels go beyond 100. Twilio’s Elastic SIP Trunking pricing page advertises unlimited call concurrency with no per-channel fee; extra calls-per-second capacity is priced separately, and its real short-call cost driver sits in criterion four. Confirm the channel ceiling in writing before load day, and keep a second trunk configured for failover so a cap never becomes a dead floor.
4. Billing increments — where the 60/60 math bites
Twilio’s help center says its voice and calling products bill any partial minute as a full one: a 61-second call bills as two minutes. Dialer campaigns generate thousands of short calls, exactly the workload rounding punishes: an 8-second voicemail hangup bills as a full minute under 60/60, versus 12 seconds under SIPNEX’s 12/6 (a 12-second minimum, then 6-second increments). A 32-second conversation bills as 36 seconds instead of 60.
At dialer volume, increments can outweigh headline per-minute rates. Run the math against your own ALOC.
5. A-level attestation the carrier actually controls
Under the SHAKEN standard (ATIS-1000074), A-level attestation means the originating provider knows the customer and their right to the calling number; B means it knows the customer but can’t verify their right to the number; C is a gateway signature.
What to check: who signs, and at what level. Twilio signs Elastic SIP Trunking calls under STIR/SHAKEN “to increase call answer rates,” and ties numbers to it through a Trust Hub Business Profile, per its 2021 changelog. Skyetel’s terms (section 7.3) assign an A, B or C level based on the customer’s representation that it may use the calling number. A carrier holding its own SP certificate signs directly.
Attestation alone is no shield, though: per TransNexus’s March 2026 STIR/SHAKEN statistics, 89.8% of calls authenticated by prolific robocall signers carried A-level attestation, which is why analytics engines also weigh calling behavior. The A-level vs. B-level breakdown covers what terminating carriers do with each.
6. Short-duration and pre-authorization clauses
voip.ms’s terms of service require pre-authorization for all telemarketing-type use — automated dialers, call centers, dialer traffic — and let voip.ms suspend unauthorized use without prior notice, DIDs included. The same terms separately require pre-authorization for short-duration calls, defined to include calls carrying signal for under six seconds. Clauses like these only become traps when you skip them and load a campaign. If a candidate’s terms carry one, get the authorization in writing before the first dial.
7. US route quality and PDD
Everything above is contractual; this one is empirical. Post-dial delay, early-media handling, ASR stability across a full campaign day, spam-label churn on the route — none of it shows up in terms of service. Run a pilot on real leads before committing volume, and measure from your VICIdial reports, not the carrier’s dashboard.
How the carrier categories score for VICIdial
UCaaS unlimited seats (RingCentral, Vonage, 8x8): fail criterion one — the policies quoted above rule out the workload. An unlimited plan pointed at a dialer is a suspension with a start date; the pricing math is laid out in why unlimited plans ban auto dialing.
CPaaS platforms (Twilio, Telnyx): engineering-grade networks with real documentation, but read criteria 1, 2 and 4 closely. Per-minute rounding taxes every short call, and CPS beyond a small free allotment costs extra. The written dialing policy differs by platform: Twilio’s Acceptable Use Policy has no autodialer prohibition and instead requires consent and opt-out compliance, while Telnyx’s lists predictive dialing among improper uses and sets its own ASR and abandoned-call thresholds.
Budget wholesale ITSPs (voip.ms, Skyetel, Flowroute): the rates attract dialer operators, so score criteria 1 and 6 before anything else. voip.ms demands pre-authorization. Skyetel’s terms (section 7.2) don’t prohibit dialer traffic; they make you solely responsible for TCPA compliance, with consent records kept at least five years and full indemnification. Flowroute’s terms of use require compliance with the TCPA and the FCC’s telemarketing rules and take no dialer-specific stance. They are not interchangeable.
Dialer-grade carriers (SIPNEX — bias fully disclosed): the category built for the workload, and we’re in it. SIPNEX is an FCC-licensed carrier: VICIdial traffic is the accepted use, not a tolerated one. Billing is 12/6 on dialer traffic, calls are signed under our own STIR/SHAKEN SP certificate at A-level attestation, and we’re registered in the Robocall Mitigation Database (a filing the FCC requires of every provider).
SIPNEX publishes its per-minute tiers on its pricing page, and the published band is a ceiling: increments and traffic mix vary, so clean traffic profiles are quoted below it against actual CDRs. Config lives in the VICIdial SIP trunk setup guide.
Red flags that predict a mid-campaign suspension
- “Unlimited” anywhere in the plan name. Unlimited pricing depends on light usage; a dialer is the opposite, and the unlimited terms quoted above either exclude autodialing or limit use to normal business calling.
- Prohibited-use language you’re planning to ignore. Traffic flowing today means nothing — the clause activates when your volume gets noticed.
- Discretionary thresholds. Action on “low ASR” or abandonment “as determined by” the carrier makes your campaign metrics grounds for termination at someone else’s judgment.
- Pre-authorization clauses you never invoked. Suspension can arrive without prior notice, taking your DIDs with it.
- Attestation by paperwork. If your signature level rests on representations, verify what your calls actually carry.
If a suspension lands anyway, the dialer account suspension playbook covers the recovery sequence — but the scorecard exists so you never need it.
Frequently asked questions
Can I run VICIdial on an unlimited VoIP plan?
Not safely. The unlimited terms quoted above either bar autodialing outright or limit use to normal business calling. RingCentral’s AUP prohibits predictive dialing, Vonage names auto-dialing and call-center use as impermissible on residential unlimited plans, and 8x8’s archived Business Terms exclude autodialing from Unlimited PSTN plans with immediate-termination rights. Metered, dialer-grade trunking is the durable model.
How much CPS does a VICIdial floor actually need?
Estimate it from your own campaigns: agents × dial ratio ÷ attempt spacing sets the burst rate, and hopper refills spike it. Then compare against the carrier’s written default — Telnyx, for example, documents 20 CPS per source IP with excess attempts rejected. Get your required CPS confirmed in writing before load day, not mid-campaign.
Does A-level attestation guarantee VICIdial answer rates?
No. A-level attestation is necessary hygiene, not a deliverability guarantee — per TransNexus’s March 2026 STIR/SHAKEN statistics, 89.8% of calls authenticated by prolific robocall signers carried A-level attestation, so analytics engines weigh volume and duration behavior alongside the signature. B attestation reads as a lower-trust signal, but no carrier publishes a specific answer-rate gap.
Score your current trunk against the seven criteria — if it fails two or more, run a pilot before your carrier runs the clause. SIPNEX quotes VICIdial-grade trunking against actual CDRs: (833) 665-2220.
Keep reading.
The carrier built by operators, for operators.
FCC-licensed carrier with its own STIR/SHAKEN SP certificate. Operator-owned. SIP trunks built for operators who dial at volume.