This guide is built specifically for companies looking for the best SIP Trunking provider for 3CX. We’ll give you:
A certified provider shortlist based on 3CX’s Preferred and Supported lists
A clear explanation of what “Preferred” vs “Supported” actually means
Deployment-specific guidance (Hosted by 3CX vs self-hosted vs on-prem)
A practical decision framework based on your use case
Tthis article will help you shortlist the right option with confidence.
In this article:
TL;DR — Best SIP Trunking Providers for 3CX
If you’re already using 3CX, the safest path is simple:
Choose a Preferred or Supported provider listed by 3CX.
Use registration-based trunks for Hosted by 3CX deployments.
Follow the provider’s official 3CX configuration guide carefully.
Always enter your main trunk number in E164 format.
Confirm TLS support if secure signaling is required.
The “best” SIP trunk depends on your scenario:
Support teams → prioritize inbound stability and SLA clarity.
Outbound sales → prioritize caller ID flexibility and fast DID provisioning.
Multi-country businesses → prioritize DID coverage and routing redundancy.
MSPs → prioritize subaccounts, portal usability, and responsive support.
Best SIP Trunking Providers for 3CX (At a Glance)
If you don’t want to read the full breakdown yet, this table helps you quickly narrow down providers based on deployment type and feature needs.
| Provider | 3CX Status | Best For | TLS | SMS | Fax / T.38 | Key Notes (E164 / CID / Special Steps) |
|---|---|---|---|---|---|---|
| Telxi | Supported | Hosted by 3CX, global SMBs, sales/support teams | Yes | No (UK listing) | Yes (T.38 Bypass) | Registration-based recommended for Hosted by 3CX; main trunk must be E164 |
| Telnyx | Supported | US deployments, API flexibility, SMS support | Yes | Yes | Yes (T.38 Bypass) | Main trunk must be E164; supports CLIP No Screening |
| Twilio | Preferred | Developer-driven environments | No | Yes | No | No TLS; E164 required; follow 3CX config guide carefully |
| Bandwidth | Supported | US enterprise & high-volume environments | No | Yes | Yes (T.38 Bypass) | No TLS; E164 required; confirm CID policies |
| Flowroute (Intrado) | Supported | US-focused outbound teams | No | Yes | No | Dialing must be 11-digit or +E164; follow config guide |
| Gradwell | Supported | UK SMEs | No | No | No | Enter trunk in international format (e.g., 4479…); no TLS |
| Voxtelesys | Supported (region dependent) | Cost-sensitive US businesses | Yes | Yes | Yes (T.38 Bypass) | E164 required; follow configuration guide |
| Colt | Supported (region dependent) | Enterprise multi-country deployments | No | No | Yes (T.38 Bypass) | E164 required; enterprise contract model |
How We Evaluated the Best 3CX SIP Trunking Providers?
Every provider in this guide was evaluated specifically through a 3CX deployment lens, focusing on what actually affects stability, configuration time, and upgrade safety.
Here’s exactly what we looked at:
3CX certification status — Whether the provider is listed as Preferred or Supported by 3CX. Certified providers are tested for compatibility and are less likely to break after updates.
Template availability — Whether 3CX includes an official auto-configuration template. Templates reduce manual errors and prevent SIP header mismatches.
TLS / SRTP support — Secure SIP signaling (TLS) and encrypted media (SRTP) are essential for hosted and security-conscious deployments.
SMS support inside 3CX — Not all trunks support SMS integration within the 3CX interface. This matters for sales and support teams using text messaging.
Fax (T.38) compatibility — If fax is required, T.38 support and known configuration behavior are important to avoid routing issues.
E164 formatting requirements — Strict number formatting rules can cause outbound call failures. We considered how rigid each provider is and how well it aligns with 3CX normalization.
Caller ID restrictions — Some providers limit outbound caller ID to owned DIDs or require verification. This impacts outbound sales workflows.
Portal usability — Provisioning speed, DID management, subaccounts, call logs, and routing controls all affect day-to-day operations—especially for MSPs.
Pricing model clarity — Whether pricing is per-channel, metered, or hybrid. Transparent cost structure reduces surprises in high-volume environments..
Best SIP Trunking Providers for 3CX
Now that we’ve covered how 3CX classifies providers and how we evaluated them, let’s move into the actual shortlist.
These providers are either Preferred or Supported by 3CX, widely deployed in real-world environments, and suitable for different 3CX installation modes (Hosted by 3CX, self-hosted VPS, or on-prem).
Below are the best SIP Trunking providers for 3CX:
Telxi
Telxi is a global SIP trunking provider for 3CX positioned for business-grade voice infrastructure, supporting 3CX deployments across Hosted by 3CX, self-hosted VPS, and on-prem installations. It offers both registration-based and IP-based authentication, secure SIP over TLS, and global DID availability.
For 3CX users, the key advantage is straightforward configuration with registration-based trunks (recommended for Hosted by 3CX environments).
Best for
Hosted by 3CX deployments (registration-based trunks)
UK and multi-country DID requirements
SMBs with inbound support and outbound sales
MSPs managing multiple 3CX instances
3CX Status
Listed as a supported provider in the UK region by 3CX.
Capabilities (Per 3CX Listing + Product Info)
SIP TLS Support: Yes
SMS Support: No (per UK listing)
Fax Support: Yes — T.38 Bypass
Anonymous Calling: No
CLIP No Screening: No
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Available
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format (e.g., 441234567890).
Registration-based trunks are recommended for Hosted by 3CX deployments to avoid IP change issues.
Follow the official 3CX configuration template for normalization rules and outbound caller ID behavior.
Pros and Cons
| Pros | Cons |
|---|---|
| Supports TLS for secure SIP signaling | SMS not supported (per UK listing) |
| Fax supported via T.38 Bypass | Not a Preferred provider |
| Registration-based trunks (ideal for Hosted by 3CX) | No IPv6 support listed |
| Flexible authentication (IP or registration) | No CLIP No Screening |
| Online provisioning portal | |
| Transparent pricing model |
Pricing
Telxi promotes transparent, contract-free SIP trunk pricing.
Key structure highlights:
Channel-based pricing (starting from a low monthly cost per channel)
Usage-based termination rates (per minute, destination dependent)
DIDs billed monthly (varies by country)
This flexible structure makes it suitable for scaling 3CX deployments without locking into high minimum commitments.
Telnyx
Telnyx is a global SIP trunking provider known for API-driven telephony and strong North American coverage. It is widely used in cloud-native and hybrid deployments, including 3CX installations that require TLS support, SMS capability, and flexible caller ID control.
For 3CX users, Telnyx is often chosen for its feature depth and programmable infrastructure.
Best for
US-based 3CX deployments
Businesses needing SMS support inside 3CX
Outbound-heavy teams requiring caller ID flexibility
Hybrid or API-driven environments
3CX Status
Listed as a supported provider in the USA region by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: Yes
SMS Support: Yes
Fax Support: Yes — T.38 Bypass
Anonymous Calling: Yes
CLIP No Screening: Yes
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format.
Caller ID flexibility is supported, but normalization rules should be aligned with 3CX outbound formatting.
Follow the official 3CX configuration template to avoid SIP header mismatches.
Pros and Cons
| Pros | Cons |
|---|---|
| SMS supported inside 3CX | Can be more complex than plug-and-play providers |
| TLS and SRTP support | Pricing can scale quickly with usage |
| Fax supported via T.38 Bypass | API-centric platform may be overkill for simple setups |
| Supports CLIP No Screening | |
| Anonymous calling supported | |
| Strong portal and API control |
Pricing
Telnyx uses a usage-based pricing model for elastic SIP trunking.
Key structure elements:
Metered inbound and outbound call pricing
Per-number monthly DID fees
No traditional per-channel fixed model (elastic scaling)
Pricing varies by destination and call type
Twilio
Twilio is a cloud communications platform widely known for APIs and programmable voice infrastructure. Its Elastic SIP Trunking product is often used by developer-driven teams that want flexible, usage-based telephony inside custom applications and cloud environments.
For 3CX users, Twilio can work well — but it typically requires closer adherence to configuration documentation compared to more PBX-oriented carriers.
Best for
Developer-led organizations
API-centric voice environments
Businesses already using Twilio messaging or other Twilio products
US-based 3CX deployments needing SMS support
3CX Status
Listed as a preferred provider in the USA region by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: No
SMS Support: Yes
Fax Support: No
Anonymous Calling: Yes
CLIP No Screening: No
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format.
Be sure to follow the official 3CX configuration guide carefully.
TLS is not supported per 3CX listing, so signaling will rely on non-TLS transport.
Pay close attention to caller ID formatting and SIP policy configuration.
Pros and Cons
| Pros | Cons |
|---|---|
| SMS is supported inside 3CX | No SIP TLS support (per 3CX listing) |
| Strong developer ecosystem | No fax/T.38 support |
| Flexible, elastic scaling model | Not optimized specifically for PBX-first deployments |
| Robust online portal and APIs | May require careful SIP policy configuration |
| Widely recognized platform | Usage-based pricing can become unpredictable |
Pricing
Twilio Elastic SIP Trunking follows a usage-based model:
Metered inbound and outbound call pricing
Monthly trunk and DID fees
No fixed per-channel pricing — scaling is elastic
Additional costs may apply for advanced features or regional routing
Bandwidth
Bandwidth is a US-based carrier and SIP trunking provider that operates its own nationwide IP voice network. It is often selected by enterprises and high-volume environments that want direct carrier control rather than a pure reseller model.
For 3CX deployments, Bandwidth is commonly used in US-based installations where SMS support, caller ID flexibility, and T.38 fax compatibility are required.
Best for
US-based 3CX deployments
High-volume inbound and outbound environments
Enterprises needing direct carrier infrastructure
Businesses requiring SMS and fax support
3CX Status
Listed as a supported provider in the USA region by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: No
SMS Support: Yes
Fax Support: Yes — T.38 Bypass
Anonymous Calling: Yes
CLIP No Screening: Yes
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format.
Be sure to follow the official 3CX configuration guide for normalization and routing.
TLS is not supported per 3CX listing, so signaling will rely on non-TLS transport.
Caller ID behavior should be aligned with 3CX outbound formatting rules.
Pros and Cons
| Pros | Cons |
|---|---|
| SMS supported inside 3CX | No SIP TLS support (per 3CX listing) |
| Fax supported via T.38 Bypass | Primarily US-focused coverage |
| Supports CLIP No Screening | Pricing often quote-based |
| Carrier-owned network infrastructure | May require configuration guide adherence |
| Online portal for number and trunk management |
Pricing
Bandwidth typically operates on a usage-based pricing model with optional channel-based structures depending on the contract.
Pricing structure generally includes:
Monthly DID fees
Metered inbound and outbound call charges
Potential volume-based pricing tiers
Enterprise or contract-based pricing for larger deployments
Flowroute (Intrado)
Flowroute, now part of Intrado, is a US-based SIP trunking provider focused on programmable voice and messaging services. It is commonly used by SMBs and technical teams that want flexible SIP connectivity with SMS capabilities and a self-service portal.
For 3CX deployments, Flowroute is often selected for US-focused environments where outbound flexibility and SMS support matter more than advanced enterprise routing features.
Best for
US-based 3CX installations
Outbound sales teams need caller ID flexibility
Businesses requiring SMS support
Technical teams comfortable following configuration guides
3CX Status
Listed as a supported provider in the USA region by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: No
SMS Support: Yes
Fax Support: No
Anonymous Calling: Yes
CLIP No Screening: Yes
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format.
Dialing must be in either 11-digit format (e.g., 17778811960) or full +E164 format (+17778811960).
Be sure to follow the official 3CX configuration guide carefully.
TLS is not supported per 3CX listing, so signaling uses non-TLS transport.
Pros and Cons
| Pros | Cons |
|---|---|
| SMS supported inside 3CX | No SIP TLS support (per 3CX listing) |
| Flexible outbound caller ID | No fax/T.38 support |
| Supports CLIP No Screening | Primarily US-focused |
| Self-service online portal | Requires strict dialing format compliance |
| Usage-based pricing model |
Pricing
Flowroute uses a usage-based pricing model:
Monthly DID charges
Metered inbound and outbound call rates
No traditional fixed channel requirement
Pricing varies by destination and call type
Go to Pricing Page
Gradwell
Gradwell is a UK-based business communications provider offering SIP trunks and hosted telephony services. It is commonly used by UK SMEs that prefer working with a local provider and value traditional business telephony support.
For 3CX deployments, Gradwell is typically selected in UK-based installations where local number provisioning and straightforward SIP connectivity are the priority.
Best for
UK-based 3CX deployments
SMEs wanting a UK-focused provider
Businesses prioritizing local support over global expansion
3CX Status
Listed as a supported provider in the UK region by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: No
SMS Support: No
Fax Support: No
Anonymous Calling: Yes
CLIP No Screening: No
IPv6 Ready: No
Online Sign-Up & Portal: Limited (varies by service plan)
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in international format (e.g., 447975777666).
Follow the official 3CX configuration guide to ensure correct normalization and routing.
TLS is not supported per 3CX listing.
Pros and Cons
| Pros | Cons |
|---|---|
| UK-focused provider | No SIP TLS support |
| Anonymous calling supported | No SMS support |
| Suitable for local number provisioning | No fax/T.38 support |
| Supported by 3CX (UK region) | Limited portal automation |
| Familiar SME provider | Fewer advanced capabilities |
Pricing
Gradwell typically provides business SIP trunking with:
Monthly trunk or channel-based pricing
UK DID number rental
Metered inbound and outbound call charges
Voxtelesys
Voxtelesys is a US-based SIP trunking provider offering voice, messaging, and global number services. It is often positioned as a cost-effective option for SMBs that want flexible SIP connectivity with SMS support and secure signalling.
For 3CX deployments, Voxtelesys can be attractive for US-focused environments that require TLS support, SMS integration, and T.38 fax compatibility.
Best for
US-based 3CX deployments
SMBs looking for cost-sensitive SIP trunking
Businesses needing SMS + fax support
Hosted or self-hosted 3CX environments using registration-based trunks
3CX Status
Listed as a supported provider (region dependent) by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: Yes
SMS Support: Yes
Fax Support: Yes — T.38 Bypass
Anonymous Calling: No
CLIP No Screening: Yes
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format.
Follow the official 3CX configuration guide carefully.
Ensure outbound caller ID formatting aligns with 3CX normalization rules.
Pros and Cons
| Pros | Cons |
|---|---|
| TLS is supported for secure signaling | Anonymous calling not supported |
| SMS is supported inside 3CX | Primarily US-focused coverage |
| Fax supported via T.38 Bypass | Requires adherence to 3CX configuration guide |
| CLIP No Screening supported | |
| Online provisioning portal | |
| Cost-sensitive positioning |
Pricing
Voxtelesys promotes competitive SIP trunk pricing with:
Monthly DID fees
Metered inbound and outbound usage
No long-term contracts
Transparent pricing tiers are listed publicly
This makes it attractive for SMBs running 3CX who want predictable pricing without enterprise-level minimums.
Colt
Colt is a global SIP Trunking provider for 3CX across Europe, Asia, and North America. It operates its own network infrastructure and is typically selected by larger organisations that require carrier-level reliability and multi-country voice connectivity.
For 3CX deployments, Colt is generally suited to enterprise environments where stability, international presence, and structured telecom contracts matter more than rapid self-service provisioning.
Best for
Enterprise 3CX deployments
Multi-country or European-based organizations
Businesses requiring carrier-owned infrastructure
Large call volume environments
3CX Status
Listed as a supported provider (region dependent) by 3CX.
Capabilities (Per 3CX Listing)
SIP TLS Support: No
SMS Support: No
Fax Support: Yes — T.38 Bypass
Anonymous Calling: Yes
CLIP No Screening: Yes
IPv6 Ready: No
Online Sign-Up & Portal: Yes
Registration-based trunks: Supported
IP-based authentication: Supported
Important 3CX Configuration Notes
The main trunk number must be entered in E164 format.
Follow the official 3CX configuration guide for normalisation and routing rules.
TLS is not supported per 3CX listing, so signalling uses non-TLS transport.
Pros and Cons
| Pros | Cons |
|---|---|
| Enterprise-grade global infrastructure | No SIP TLS support (per 3CX listing) |
| Supports CLIP No Screening | No SMS support |
| Fax supported via T.38 Bypass | Often contract-based pricing |
| Suitable for multi-country deployments | Less self-service oriented than API-first providers |
| Online portal available |
Pricing
Colt typically operates under structured enterprise telecom agreements:
Contract-based pricing
Monthly trunk/channel charges
Usage-based call billing
Regional pricing differences
How to Choose the Best SIP Trunking Provider for 3CX?
Every provider listed here is tested and certified by 3CX, and their templates are maintained with each release to reduce compatibility issues after upgrades.
Before selecting a SIP Trunking provider for 3CX, always:
Confirm your deployment type (Hosted, self-hosted VPS, or on-prem)
Check the official 3CX listing for configuration notes
Review any formatting or dialing requirements (E164, caller ID, normalization rules)
With that foundation in mind, here’s how to choose based on your real-world use case.
Support Teams
If your 3CX system runs customer support queues, inbound stability is critical, because missed calls mean missed tickets, escalations, and frustrated customers. In this case you need a provider with consistent call routing and clear concurrency handling so you don’t hit unexpected channel limits during peak hours.
Failover capabilities also matter. If routing degrades or a trunk experiences an issue, calls should be redirected automatically. For support environments, clarity around SLA terms and escalation paths is just as important as technical compatibility.
Outbound Sales Teams
Outbound-heavy teams care about 2 important things: caller ID control and deliverability.
If your sales reps are dialing daily, you need flexibility in outbound caller ID presentation. Some providers restrict outbound numbers to owned DIDs or require verification, which can impact campaign agility.
Finally, deliverability matters. Poor routing or aggressive spam flagging can hurt connection rates. For outbound sales, you want a provider that aligns with compliance standards but still supports healthy dialing patterns.
Multi-Location / Global Businesses
If your company operates across countries, DID coverage is essential. Some providers excel in one country but have limited presence elsewhere.
Regional compliance also plays a role. Certain countries require documentation or local registration for numbers. so make sure your provider can support those processes.
Routing redundancy becomes more important at scale. Multi-location deployments benefit from providers with geographically distributed infrastructure to maintain call quality and availability.
For global environments, breadth of coverage and network stability often matter more than price alone.
Why Many Companies Using 3CX Choose Telxi?
Many companies choose Telxi because it aligns well with practical 3CX deployment needs.
One of the main reasons is compatibility with registration-based trunks, which are recommended for Hosted by 3CX environments. Since public IP changes can occasionally disrupt IP-authenticated trunks, having a provider that supports clean registration-based authentication reduces risk.
Telxi also supports SIP TLS and T.38 fax bypass, which makes it suitable for secure business environments and industries that still rely on fax workflows. While SMS support may vary by region, core SIP trunking functionality aligns well with standard 3CX configurations, including E164 number formatting.
Telxi tends to attract 3CX users who want:
Stable trunk behavior across updates
Secure signaling (TLS support)
Global DID coverage without complex contracts
A provider that doesn’t require heavy SIP debugging to maintain
FAQ Best 3CX SIP Trunking Providers
- Who are SIP trunk providers?
SIP trunk providers are telecommunications companies that connect your PBX (like 3CX) to the public telephone network using SIP (Session Initiation Protocol).
They provide:
Inbound and outbound call connectivity
Phone numbers (DIDs)
Call routing and termination
Optional features like SMS or fax support
Without a SIP trunk provider, your 3CX system cannot make or receive external calls.
- Are there any free SIP trunks?
Some providers offer trial credits or limited free tiers, but fully free SIP trunks for production use are rare.
Free options typically:
Have limited call capacity
Restrict outbound destinations
Lack SLA guarantees
Offer minimal support
For business environments, a certified and supported provider is strongly recommended.
- Does 3CX support SIP TLS and SRTP?
Yes, 3CX supports TLS for SIP signaling and SRTP for encrypted media — but compatibility depends on whether your SIP trunk provider supports those protocols. Always verify TLS/SRTP support in the provider’s 3CX capability listing.
- Can I use a SIP provider not listed by 3CX?
Yes, but it’s not recommended unless you’re comfortable manually configuring SIP settings.
Using a non-certified provider means:
No official template
No guaranteed compatibility after updates
Higher risk of formatting or routing issues
For stability — especially in production environments — stick with providers listed as Preferred or Supported by 3CX.
- Is 3CX a SIP trunk provider?
No. 3CX is a PBX (Private Branch Exchange) system — not a SIP trunk provider. It manages call routing, extensions, queues, and unified communications features.
To connect 3CX to the public telephone network (PSTN), you need a SIP trunk provider that delivers inbound and outbound call connectivity
