Fax API & Cloud Fax
Programmable fax that behaves like the rest of your stack - send and receive over REST, T.38 or email, on fax-enabled numbers in 60+ countries, with encryption and retention built for regulated industries.
60+
Countries with fax numbers
T.38
And G.711 pass-through
AES-256
Encryption at rest
What is Fax API & Cloud Fax?
Fax has not gone away. Hospitals, courts, law firms, insurers, customs brokers and government agencies still exchange millions of documents a day by fax because it is legally accepted, universally understood and does not require the other party to adopt anything new. What has changed is the expectation that fax should be as easy to automate as email or SMS. Dollu's Fax API gives developers a REST interface to send and receive faxes, while cloud fax gives business users fax-to-email and email-to-fax without a machine, a phone line or a fax server to maintain.
Sending is a single API call: post a PDF, TIFF, DOCX or image, the destination number and optional cover-page fields, and receive a job ID. We convert and render the document, place the call over our carrier network, negotiate the fax session and report progress and completion - pages sent, duration, remote fax ID and any error cause - by webhook or polling. Receiving works in reverse: fax-enabled numbers in more than 60 countries deliver incoming documents to a webhook, an email address, an SFTP folder or the portal, with the rendered PDF and metadata attached.
For organisations with existing fax servers, multifunction printers or PBX-based fax gateways, we offer T.38 SIP fax trunks with G.711 pass-through fallback, so you keep your current workflow but retire the analogue lines and the carrier that struggles with fax over IP. Sessions are negotiated with ECM and appropriate speed selection, and our voice core is tuned for fax reliability with jitter buffering and codec locking on fax-detected calls.
Because most fax content is sensitive, security and retention are first-class features. Documents are encrypted in transit and at rest with AES-256, access is controlled per user and API key with full audit logs, and retention policies can be set from immediate deletion after delivery to multi-year archives to satisfy healthcare, legal and financial-services requirements. Data-processing agreements and business associate agreements are available for customers that need them, and processing regions can be constrained to the EU or India on request.
CPaaS request and event flow: REST in, webhooks out.
Why choose Dollu for fax api.
The advantages of buying from a carrier that owns its network, interconnects and operations - rather than a reseller.
Built for healthcare workflows
Referrals, prescriptions and records move through EHR and practice-management systems over the API, with encryption, audit and retention controls that support HIPAA-aligned programmes.
Legally accepted, digitally handled
Courts, registries and counterparties keep faxing; your team gets searchable PDFs in email or the case system with delivery confirmations for the record.
Fax as just another endpoint
Same authentication, SDKs and webhook patterns as our SMS, voice and email APIs, so fax fits into existing pipelines without a specialist team.
Security you can evidence
Encryption at rest and in transit, role-based access, IP allow-lists and immutable audit logs make compliance reviews straightforward.
Retire the machines and the lines
Replace analogue lines, fax boards and on-premise fax servers with T.38 trunks and cloud fax, cutting hardware, telco rental and maintenance cost.
Capabilities in detail.
Everything included with Fax API & Cloud Fax - the platform features, options and controls you get from day one.
- 01
Send API
POST a document and destination; we render, dial and deliver with automatic retries on busy or no-answer, page-level status, remote CSID capture and configurable cover pages and header lines.
- 02
Receive API and inbound routing
Assign fax-enabled numbers to webhooks, email addresses, SFTP folders or users; route by number or DID range; receive rendered PDF plus metadata such as caller ID, page count and duration.
- 03
T.38 and G.711 fax trunks
SIP trunks tuned for fax with T.38 negotiation, G.711 pass-through fallback, ECM support and codec locking, for fax servers, MFPs and ATAs behind your PBX or SBC.
- 04
Fax-to-email and email-to-fax
Users send by emailing number@fax domain with attachments and receive faxes as PDF in their inbox; sender allow-lists, per-user quotas and delivery receipts included.
- 05
Fax-enabled numbers and porting
Local, national and toll-free numbers in 60+ countries provisioned from the portal or API; port your existing fax numbers so correspondents notice nothing.
- 06
Document handling
Accepts PDF, TIFF, DOCX, PNG and JPEG; renders to fine or standard resolution; merges multiple attachments; adds cover pages and TSI headers per account or per job.
- 07
Encryption, access and audit
AES-256 at rest, TLS 1.2+ in transit, per-user and per-key permissions, IP allow-lists, SSO for the portal and immutable audit logs of every send, view and download.
- 08
Retention and archiving
Policies from delete-on-delivery to seven-plus years; legal hold; export to your own storage over SFTP or S3-compatible endpoints; deletion certificates on request.
- 09
Reporting and alerts
Per-user, per-number and per-key volumes, success rates and failure causes; alerts on repeated failures or unusual volumes; CSV and API export for cost allocation.
How it works.
From first conversation to live traffic - a tracked, engineer-led onboarding with a named owner at every step.
- Step 01
Choose numbers or port yours
Select fax-enabled numbers in the countries you need or submit a port request for existing fax lines. Numbers are typically live the same day; ports follow the local operator timeline.
- Step 02
Pick your interface
Integrate the REST API with our SDKs, configure email-to-fax for business users, or connect your fax server or MFP over a T.38 SIP trunk - or combine all three.
- Step 03
Set security and retention
Define user roles, API-key scopes, IP allow-lists and the retention policy per number or department. Enable SSO and audit-log export if required.
- Step 04
Send, receive and monitor
Go live with test faxes to our echo numbers, then track deliveries, failures and volumes in the dashboard with webhook events feeding your own systems.
Who uses this and why.
Typical deployments across carriers, enterprises, platforms and contact centres.
Hospitals, clinics and pharmacies
Referrals, lab orders, prescriptions and prior authorisations sent and received from EHR systems with audit trails and retention aligned to health-record rules.
Law firms and courts
Filings, service of documents and correspondence with registries that still require fax, with time-stamped delivery confirmations for the file.
Banks, insurers and brokers
Signed instructions, claims documents and KYC paperwork exchanged with counterparties over encrypted fax with long-term archive.
Government and public sector
Citizen-facing departments that must accept fax alongside email and portals, consolidated into one cloud service with departmental routing.
Logistics, shipping and customs
Bills of lading, customs declarations and delivery instructions to ports, agents and brokers around the world from your TMS or ERP.
Enterprise IT retiring fax servers
Replace on-premise fax boards and servers with T.38 trunks and the API, keeping existing MFPs and workflows while removing analogue lines.
Technical & commercial specifications.
Key parameters at a glance. Ask us for the full service description and SLA document.
| Interfaces | REST API (JSON), email-to-fax/fax-to-email, portal, T.38 SIP trunk |
|---|---|
| Fax protocols | T.38 (UDPTL) with G.711 pass-through fallback; ECM; up to 33.6 kbps |
| Numbers | Fax-enabled local, national and toll-free in 60+ countries; porting |
| Documents | PDF, TIFF, DOCX, PNG, JPEG; standard and fine resolution |
| Delivery | Webhook, email, SFTP, portal; page-level status and remote CSID |
| Retries | Configurable on busy/no answer; up to 5 attempts by default |
| Security | AES-256 at rest, TLS 1.2+ in transit, RBAC, IP allow-lists, SSO |
| Retention | Delete-on-delivery to 7+ years; legal hold; export to SFTP or S3 |
| Compliance | GDPR, HIPAA-aligned controls, ISO 27001 and SOC 2 practices |
| Support | 24×7 NOC; P1 response ≤ 15 min; named account manager |
How APIs / CPaaS are priced.
APIs are usage-based: per minute, per message, per verification, per participant-minute or per email - at carrier pricing, because Dollu’s own network sits underneath the endpoints.
We publish the model, not a public rate card - actual rates depend on destination, route class, volume and regulatory cost. See how every Dollu service is priced.
- Free sandbox for development and testing
- Sub-account and reseller rate decks
- Committed-spend discounts by monthly usage
- No platform fee at entry volumes
- Numbers added at rental + usage
- Billing
- Metered per unit; prepaid balance or postpaid invoicing; usage visible in real time in the portal and API
- Commitment
- None; committed monthly spend earns tiered discounts
Fax API - your questions answered.
The questions customers and carriers ask us most often before they interconnect. If yours is not here, our team answers within one business day.
Still have a question?
Ask our solutions teamRelated services.
Services customers commonly combine with Fax API & Cloud Fax.
Send your first fax from code today.
Request API keys and a test fax number; our developer support team will help you send and receive your first documents within the hour.
