Telnyx fax alternative
Telnyx Programmable Fax supports sending and receiving, with controls for fax transmission and a per-page charge plus SIP trunking usage. mintfax sends faxes only, with automatic retries and no fax number rental required to send.
Feature comparison
| Feature | Telnyx Programmable Fax | mintfax |
|---|---|---|
| API style | REST/JSON | REST/JSON |
| Base URL | https://api.telnyx.com/v2 | https://api.mintfax.com/v1 |
| Auth | Bearer token (V2 API key from Mission Control) | Bearer token; environment inferred from key prefix |
| Environment scoping | V2 API key generated in Mission Control Portal | mfx_test_, mfx_live_, mfx_acct_ |
| Prerequisites to send | Account + phone number + Fax Application + V2 key | Account + sandbox API key |
| Per-page price | $0.007/page + SIP trunking usage | $0.060 standard; $0.048 at 100k+/mo; $0.036 at 1M+/mo |
| Phone number rental | $1/mo per US local number (a number is required to send) | Not required; mintfax assigns origination |
| BAA | Through sales; public guidance frames services under conduit exception | Free BAA in the dashboard; separate DPA |
| Zero-footprint / PHI deletion | Not documented as a product toggle | Opt-in zero-footprint mode; 30-day content retention default (7-365) |
| Webhook signing | Ed25519, header telnyx-signature-ed25519, per-account public key | HMAC-SHA256 per Standard Webhooks; per-endpoint whsec_ secret |
| Idempotency on send | Not documented | Idempotency-Key header; 24h expiry; 409 on reuse |
| Auto send retries | None; customer implements | 1m / 3m / 5m / 5m, default 3 attempts, per-fax max_attempts 1-5 |
| Webhook retries | At least one retry per URL, then failover URL; 2s response timeout | 3 retries at 10s / 60s / 300s, then stop |
| Error model on send | 14-code flat failure_reason on the fax.failed payload | 17 API error codes + 10 delivery error codes + optional error_subcode |
| Request tracing | Not documented | X-Request-Id: req_<ULID> on every response; echoed as request_id |
| Sandbox | No sandbox documented | Nine test numbers covering nine scenarios; same API as live |
| Per-fax carrier controls | T.38 toggle, monochrome, black threshold, quality ladder | Not exposed |
| File upload | Multipart (contents, up to 20 MB) or URL fetch (media_url, 50 MB) | Multipart file upload, 10 MB |
| File formats | PDF, DOCX, XLSX, JPG, PNG, TIFF, HTML, plain text | |
| Inbound / receive | Yes (Fax Application concept for inbound routing) | No (outbound only) |
| Cancel a queued fax | POST /v2/faxes/{id}/actions/cancel | No cancel endpoint |
| Category | Multiple communications services | Fax-only |
Sending and retries
Telnyx requires an account, a phone number, a Fax Application, and an API key before you send. With mintfax, you register and verify your email to get a sandbox key. You do not need to buy a fax number.
Telnyx expects your application to retry failed outbound faxes. mintfax retries automatically, with three attempts by default and a configurable limit of one to five. The delays between attempts are one, three, five, and five minutes.
Telnyx’s public fax documentation does not describe an idempotency key. mintfax accepts an Idempotency-Key on send requests for safe retries of the same request within 24 hours.
Testing and delivery errors
Telnyx’s getting-started guide uses production credentials; it does not describe a separate fax sandbox. mintfax provides nine test numbers for repeatable success and failure scenarios. Sandbox deliveries and payments are simulated.
Both APIs report delivery failures. Telnyx uses failure_reason values in its fax webhook payloads. mintfax separates request errors from delivery errors and includes a request ID for troubleshooting. See the error guide.
Agreements and data handling
Telnyx directs questions about BAAs to sales. mintfax offers a BAA and a separate DPA in the dashboard, with signed PDFs available immediately.
mintfax’s default content retention is 30 days, configurable between 7 and 365 days. Zero-footprint mode deletes patient information after delivery or failure. See compliance for details.
Other requirements
Telnyx supports inbound fax, larger uploads, and per-fax transmission settings. It also offers other communications services. mintfax does not receive faxes, and its upload limit is 10 MB.
Compare the full cost of Telnyx’s per-page charge, SIP usage, and number rental with mintfax’s per-page rates. If you decide to switch, use the Telnyx migration guide.