Confirmed

• http://www.transcom.net IPtransit is a Global voip transit network that supports T.38 by default for fax, (or G711 if that isnt suitable) PAYG if required
• http://www.thinktel.ca Canadian Origination & Termination, We support T.38 for both Orignation and Term Contact stephen.halliday@thinktel.ca
• FaxDigits - Free personilised US FAX number in Iowa State. Fax to email attachment service in pdf format. Unlimited incoming number of faxes. VOIP T.38 codec enabled for internet faxing reception.
• GAFACHI (United States) - Pay-As-You-Go SIP provider, allows you to choose your method of fax, including T.38, through your on-line account management portal.
  • Note: you can sign up for an account with Gafachi without providing any payment information (ie credit card). Once signed up, you are able to see a lot more information. (Of course you can't actually use the service until you supply payment information.)
  • There is confirmation that GAFACHI's T.38 service works with OpenPBX.
• NodePhone (Australia) - acknowledged in their FAQ that they support t.38 fax relay
• TOUBATEL (France) - Toubatel is supporting T.38 fax outbound and inbound.
• SWISSIPCOM(Switzerland) - SwissIPcom support T.38 faxing for outbound and inbound to all over europe and the US, we are terminating over 30,000 faxes every month over T38 protocol without a problem.
• Premier Voice(USA) - All Premier Voice traffic is terminated directly to the PSTN for the highest quality service possible.
• OMEGA Telecom(Cyprus) - Premium Quality Worldwide Termination with CLI and T.38 fax support. T.38 Fax DID numbers origination and Fax2Email (T.38 and G.711) Service.
• WTS Telecom T.38 with G.711 failover Worldwide Termination for VoIP Fax. Support ATAs for termination. Fax Wholesale. Fax Blasting is allowed.

Alternatives

• SatFax Networks (Canada) - SatFax Networks has a new method for fax over VoIP that is more reliable than using standard T.38. SatFax Fax Terminal Adapters will work over any form of High Speed Internet connection including Wireless Internet, Cellular Internet, and all bands of Satellite Internet services.

Crippled

• Packet8 (United States) - Packet8 now support T.38 faxing service, although only with the provider-supplied ATA device ("The Packet8 fax plans are currently only available to Packet8 existing customers who purchase a new BPA410 phone adapter for Fax Extension"). For more info. Click Here.

• BroadVox has T.38 support which was once reported to work with t38modem, but will no longer work with new accounts. You need a cryptographic credential which is entombed in the ATA they ship you, and the company is quite stubborn about never releasing that credential to the customer. So, basically, it's only T.38 if you use their ATA, and they're doing their darndest to use crypto to keep it that way.

• Draytel (UK) - acknowledged in their FAQ that they support t.38 fax relay. In conjunction with a HT386 and an SPA-2102, I have used them without any problems to transmit faxes to the US. Rate is about $0.02 per minute, pay as you go. You can test it for free (no commitment) with a two port FXS T.38 compliant ATA (HT386, SPA2102) and two different draytel accounts. Update (June 2007) DrayTEL has confirmed that they do not support T.38 on PSTN calls (see comment below)

Rumored

• MondoTalk - World wide T.38 support. Inbound and Outbound. Clear quality, Low rates. Call plans for many countries including utimed calls for Australia. No access fees, No contracts, No cancellation fees, No flag falls and No Connection fees. Too many features to mention here. (no mention of T.38 anywhere on their site)
• FreeDigits (United States) - Rumored outbound-only support for T.38 SIP through faxdigits.com server ("recommends T.38-compatible adapter for outbound" but does not promise T.38 support). inbound faxes are converted to .pdf e-mail attach by the server
• Lingo
• SunRocket
• Iristel website indicates that their adapters include T.38 support, but does not state that the service actually includes it. 100% Canadian Telephone Company. Unlimited Extended plan from $15.95. Iristel seamlessly bridges the gap between IP networks and the PSTN. Iristel's VoIP solution is ideal for Calling Card, VoIP carriers, CLEC's, Asterisk owners and virtual carriers requiring local service within Canada. Iristel also offers virtual T.38 faxing solutions both inbound & outbound.
• Gradwell - UK provider, website states that faxing is possible with a Sipura SPA 2002 and Peter Gradwell informs me that their SIP termination service supports it (and it is untested with their IAX termination service).

Disconfirmed

• teliax
• iaxtel
• Voicemeup
• Talkin2ya/Budgetphone (Netherlands) - say in their FAQ (in Dutch) that they support t.38 fax relay, however, a call to their help desk (december 2006) revealed that they do not support T38, in spite of what is mentioned their FAQ.

Wanted

• Providers offering both IAX-voice and T.38 (ie T.38 over SIP or H.323 — not necessarily over IAX)
• Pay-As-You-Go providers with T.38
• Bandwidth.com T.38 Support