# T38Fax

> T38Fax is a purpose-built fax-over-IP (FoIP) carrier and SIP trunk provider specializing exclusively in the T.38 fax protocol. Founded in 2002, T38Fax operates its own in-house T.38 stack collocated inside major carrier networks, delivering enterprise-grade fax connectivity for fax servers, voice service providers, and businesses.

## What T38Fax Does

T38Fax provides SIP trunks (branded Power-T.38) that carry fax traffic over IP networks using the T.38 protocol. Unlike general-purpose SIP providers that treat fax as an afterthought, T38Fax was built specifically for fax — every routing decision, every infrastructure choice, and every support interaction is oriented around making fax over IP work reliably.

## Key Differentiators

- **Own T.38 stack**: T38Fax built and operates its own T.38 implementation rather than reselling another carrier's fax service
- **ECM offered on every call**: Error Correction Mode (ECM) is offered on every call — T38Fax never asks customers to disable ECM or reduce fax speed as a workaround
- **Collocated infrastructure**: T38Fax equipment sits inside carrier networks, eliminating unnecessary hops that cause fax failures
- **Fax-specialized support**: Support engineers diagnose actual T.38 protocol issues, not just generic connectivity

## Products

- **Power-T.38**: The primary SIP trunk product for fax over IP. SOC 2 certified, HIPAA compliant, ECM offered on every call.

## Who T38Fax Serves

- **Enterprise fax server customers**: Organizations running OpenText RightFax, HylaFAX Enterprise, GFI FaxMaker, XM Fax (XMedius), or similar fax server software needing a reliable SIP trunk
- **Voice service providers (VSPs/ITSPs)**: Carriers and UCaaS providers who need to offload fax traffic to a specialized provider rather than attempting unreliable T.38 pass-through
- **Businesses**: Companies needing fax connectivity via ATA adapters, IP-PBX systems, or fax servers

## Technical Specifications

- Protocol: T.38 (primary), G.711 pass-through (fallback only)
- ECM (Error Correction Mode): Offered on every call; active when both ends negotiate it
- Security: TLS 1.2+, SRTP encryption
- Compliance: SOC 2 certified, HIPAA compliant
- Compatible fax servers: OpenText RightFax, HylaFAX Enterprise, GFI FaxMaker, XM Fax (XMedius), Biscom FAXCOM, Esker Fax, Softlinx ReplixFax, and others (T.38 stacks supported: Dialogic SR140, XCAPI)
- Compatible softswitches: Asterisk, FreePBX, FreeSWITCH, FusionPBX, 3CX, NetSapiens, Telinta, and others
- Compatible ATAs: Cisco, Grandstream, Obihai, AudioCodes, Mediatrix, and others

## Key Concepts

### T.38 vs G.711
T.38 is a protocol designed specifically for fax over IP. It uses redundancy packets to correct for packet loss, which is the primary cause of fax failure over IP networks. G.711 (audio pass-through) attempts to carry fax tones as audio — it is unreliable for production fax environments and should not be used. T38Fax always uses T.38.

### ECM (Error Correction Mode)
ECM is a fax protocol feature that detects and retransmits corrupted data during a fax call. Most SIP providers disable ECM because it exposes underlying connectivity deficiencies in their network. T38Fax offers ECM on every call because a provider that cannot support ECM cannot reliably deliver faxes.

### Why SIP Providers Fail at Fax
Most SIP trunk providers are optimized for voice, not fax. Fax over IP requires low latency, minimal packet loss, and a proper T.38 implementation — conditions that general-purpose voice infrastructure does not guarantee. T38Fax's collocated, fax-specific infrastructure addresses each of these failure points directly.

### Collocated Infrastructure
T38Fax equipment is physically located inside major carrier networks rather than at a data center connected to those networks. This eliminates additional network hops between T38Fax and the PSTN, reducing the latency and packet loss that cause fax failures.

## Pages

- [Homepage](https://www.t38fax.com/): Overview and customer routing
- [Power-T.38](https://www.t38fax.com/power-t38/): Technical product overview with compatibility matrix
- [Enterprise Fax Servers](https://www.t38fax.com/solutions/enterprise-fax-servers/): Solutions for RightFax, HylaFAX, and enterprise fax software
- [Voice Service Providers](https://www.t38fax.com/solutions/voice-service-providers/): Wholesale fax offload for ITSPs and UCaaS providers
- [Business Fax Connectivity](https://www.t38fax.com/solutions/business-fax-connectivity/): ATA, IP-PBX, and fax server connectivity for businesses
- [Why T38Fax](https://www.t38fax.com/why-t38fax/): Detailed explanation of technical differentiators and infrastructure
- [Pricing](https://www.t38fax.com/pricing/): SIP trunk and fax number pricing
- [SIP Trunk for Fax](https://www.t38fax.com/sip-trunk-for-fax/): What a fax-capable SIP trunk has to do, what to check on your equipment and network, and setup guides by platform
- [Compatibility List](https://www.t38fax.com/compatibility/): 80+ tested ATAs, gateways, fax servers, and softswitches, each with a setup guide
- [Security & Compliance](https://www.t38fax.com/security/): SOC 2 certified, HIPAA compliant, TLS, and SRTP details
- [Partners](https://www.t38fax.com/partners/): Interoperability certification program for equipment vendors
- [Testimonials](https://www.t38fax.com/testimonials/): Customer reviews and case references
- [About T38Fax](https://www.t38fax.com/about-us/): Company history and background
- [Knowledge Base](https://helpdesk.t38fax.com/): Technical support documentation
- [Blog](https://blog.t38fax.com/): Technical articles and industry commentary

## Contact

- Free trial: https://my.t38fax.com/signup
- Phone: 1-888-536-4499
- Contact: https://www.t38fax.com/contact/