mintfax vs. Telnyx Programmable Fax

The headline gap

Telnyx publishes the cheapest per-page rate of any major fax API: $0.007. The catch is in the Telnyx Help Center, last updated January 7 2026: “Retries for outbound faxes, which may result in an error must be configured on the client application; Telnyx does not automatically retry faxes with errors.”

So you build your own retry orchestration: the queue, the exponential backoff, the per-error-code retry policy (because some failures are retryable and some aren’t), the dead-letter queue for permanent failures, the idempotency to prevent double-sends when your retry logic intersects with HTTP retries from your callers. Telnyx will give you the granular T.30 codes you need to do this well; what they won’t do is the work.

mintfax retries up to 8 times by default, with exponential backoff, and exposes the same T.30-level diagnostics so you can override or disable retry on a per-fax basis when needed. The retry loop ships with the API.

Feature comparison

Verified against Telnyx product, developer, and help-center documentation, May 2026. Telnyx pricing: the per-fax-page rate is documented at $0.007; SIP trunking minute pricing varies by call duration and destination, with US domestic rates starting at $0.0035/min outbound.

What Telnyx still does well

Telnyx’s per-page rate is genuinely the cheapest in the market - if your team has the engineering bandwidth to absorb the orchestration cost. At very high volume (5M+ pages/month) with mature internal SRE practice, the math can work in Telnyx’s favor.

Telnyx’s T.30 diagnostic depth is the best in the category. They expose granular protocol-level codes (timer T2 expiration, modem training failures, ECM negotiation errors) that no other API matches in detail. mintfax surfaces these too, normalized into a stable taxonomy, but Telnyx is the upstream source for that depth.

Ed25519 webhook signing is cryptographically stronger than HMAC-SHA256. Both are production-grade in 2026; if your security team has a specific preference for elliptic-curve signing, Telnyx is the only major fax API offering it.

Telnyx has fax coverage in 90+ countries with carrier relationships across most of the developed world. mintfax launches with US coverage and expands; if your immediate need is fax to Brazil, Japan, or Germany, Telnyx is the more complete fit today.

The migration story

Migrating from Telnyx to mintfax is mostly about ripping out the retry orchestration code you wrote because Telnyx wouldn’t.

What changes for the dev:

• Base URL: https://api.telnyx.com/v2/faxes becomes https://api.mintfax.com/v1/fax.
• Authentication: Both use Authorization: Bearer .... The token shape is different but the header is identical.
• File formats: if your current pipeline converts to PDF specifically because Telnyx is PDF-only, you can skip that step. mintfax accepts DOCX, XLSX, HTML, and others natively.
• Retry orchestration: delete it. Configure mintfax’s built-in retry per fax submission with the retries parameter (default 3, max 8).
• Idempotency: add the Idempotency-Key header on POSTs to prevent double-sends.
• Webhook signing: mintfax uses HMAC-SHA256; Telnyx used Ed25519. The verification code looks different but the conceptual shape is the same.