Fax Over IP, Done Right.
The T.38 Carrier Built by Fax Experts.
Most SIP providers treat fax as an afterthought. We built our entire network around it — ECM enabled, T.38 stack our own, support from engineers who've spent their careers on fax.
- 30-day free trial
- No credit card required
- Unlimited support included
- 100% money-back guarantee
Trusted by teams at
Most T.38 failures trace back to the same source: voice carriers who don't control their own T.38 infrastructure, disable ECM to reduce processing load, and can't diagnose issues because the fax stack isn't theirs. When something breaks, the answer is always the same — lower your fax speed and try again. T38Fax is built differently.
Why T38Fax Works When Others Don't
Three things that separate a fax-native carrier from a voice carrier with a fax module bolted on.
Our Own T.38 Stack
We don't resell a carrier's T.38 service. We built our own infrastructure, colocated inside carrier networks, terminating G.711 to the PSTN over a single optical hop. Your calls reach our gateways every time — no upstream handoff, no variable routing, no mystery carrier.
How it worksECM on Every Call
Error Correction Mode is the part of the fax protocol that detects corrupted pages and requests retransmission. Most carriers disable it to reduce load. Without ECM, a fax "succeeds" while arriving unreadable — and neither party knows. We insist on ECM for every call, without exception.
Test your current providerSupport That Diagnoses
Our team are fax industry veterans who troubleshoot with protocol traces and T.30 analysis. When you open a ticket, you reach someone who can tell a T.38 negotiation failure from a misconfigured ATA — and fix it. Unlimited support is included on every plan, free trial through enterprise.
Visit the knowledge baseBuilt for Your Deployment
T38Fax serves fax server operators, VoIP service providers, and businesses replacing POTS lines. Each use case is handled differently — here's how.
Enterprise Fax Servers
Running RightFax, XMedius, HylaFAX, or GFI? We provide SIP trunks configured specifically for fax server environments, with full compatibility documentation and setup support.
Fax server trunksVoice Service Providers
Offload your fax traffic to a carrier whose T.38 actually works. We interconnect directly with your platform, handle the PSTN termination, and remove fax reliability as a customer service problem.
Provider offload trunksBusiness Fax Connectivity
Moving away from POTS lines, or fax broke when you switched to VoIP? T38Fax connects fax machines, ATAs, and IP-PBXs to reliable SIP trunks with setup guides for every major device.
Business fax trunksDoes Your T.38 Provider Have ECM Enabled?
ECM — Error Correction Mode — is the mechanism that confirms the image you send is the image your recipient receives. Without it, a fax can arrive with blank lines, garbled text, or missing pages while the confirmation shows "success." Most T.38 providers disable it. Take our free test and find out in under two minutes.
Free. No signup required.
"We've sent several million faxes since migrating to T38Fax, and we've not had a single demonstrable case where faxes fail when using T38Fax but succeed with our previous carrier."