Retarus Enterprise Fax APIs
For developers who want more than just an interface

Sending and receiving faxes with your application just got super smart.

Whether mobile apps or web applications—Retarus enterprise fax APIs help you find the right interface for your development environment. And best of all, they offer all the key things you need to successfully use fax services: a powerful infrastructure, international availability, and numerous customization options to fit your business operations.

Developer friendly and intuitive

Send faxes from your web or mobile application now. Simple and reliable.
Via REST API, SOAP API or alternatively via FTP or SMTP. It’s quite easy. A few lines of code, and you’re ready to go:

Reports can be sent via email or through an http web service. For additional sending options you can refer to the following WSDL:

To send a fax using FTP you just need to load on the Retarus FTP server the fax document (e.g. minimal.pdf) and an XML file in the format. The XML file supports most of the options available in other APIs for personalizing each sending. Reports can be retrieved through the same FTP interface.

Through Retarus Mail2Fax it is possible to send faxes manually through any email client, or in batch by connecting your application through SMTP to the Retarus infrastructure.

Alternatively, a distribution list can be defined as a text file and the message will be sent to all recipients in the list. In this case the destination email address is:

A report will be returned to the sending email address. Further options can be specified by inserting tags in the subject line, for example:

[PRIO:URGENT]: requires an express transmission
[ATTONLY:ON]: only the attachments, not the body of the email, will be sent as fax
[RES:HIGH]: The fax will be sent in high resolution.

Call fax transmission with “all options”:
Call fax receipt:

Discover the benefits of Retarus enterprise fax APIs.

Excellent transmission rate

Lower the failure rate of fax transmission by up to 10%. Retarus' never busy technology ensures that multiple fax jobs are never sent to one recipient simultaneously, meaning they can't block each other from being received and you don't need as many resources for manual refaxing.

Intelligent routing

Achieve up to 30% more throughput. Retarus carrier management automatically uses the carrier whose line quality and availability best matches your fax job.


Scalable and flexible

Prevent over and under utilization of capacity. With the Retarus Global Delivery Network you can send 1,000 faxes today and 1,000,000 tomorrow.

Highly available and global

Rely on global availability of reliable transmission. The Retarus Global Delivery Network has its own data centers in Europe, Asia, and the USA, offering maximum international availability. 24/7.

OCR and barcode recognition

Seamlessly integrate faxing into your workflow. For example, pre-sort, forward, save, or automatically process incoming orders using defined parameters.

Perfect integration

SAP and ERP, CRM systems, Office 365 or G Suite. Retarus Fax Services can be integrated in almost any application, via standard interfaces and API. And it's so easy for your employees to send and receive faxes with their email client or a multifunction device.

Even more benefits for you …

Monitoring and analysis

Monitor the success of your fax transmission and ensure the quality of your data easily with dashboards in the web-based Retarus administration portal. In real time and over longer periods of time.

Completely transparent costs

Reduce your process costs. The Retarus pay-per-use billing model uses fixed page pricing, regardless of the duration of transmission. No additional costs for servers, maintenance, or negotiations with carriers. We bill according to client or cost center upon request.

Security and compliance

PGP and X.509 encryption

Protect yourself in the best way possible when transmitting fax messages. We don't just transmit your faxes with encryption to the Retarus infrastructure. We can also encrypt and sign each individual incoming and outgoing fax for you.

Long-term archiving

Comply with legal requirements. Retarus' long-term archiving helps you comply with the most stringent data security and integrity requirements.

Enterprise-level SLAs

Choose a service level agreement that meets your needs in terms of quality and response time. Retarus fax APIs are suitable for startups, mid-sized companies, and international enterprises.

Telephone number service

Receive fax documents anywhere. Retarus provides you with your own incoming fax numbers on any continent and ports your existing telephone numbers.

Service and support

Experience first-class support. The Retarus Team for Enterprise Fax APIs is here to answer your questions and tailor a solution to meet your needs.

Count on quality.


Facilitate and optimize order and delivery processes.

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Health Care

Transmit confidential lab data quickly and reliably.

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Map OTC trading efficiently and according to regulations.

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Expect more.

The Retarus Global Delivery Network is a unique global infrastructure for reliable information logistics via fax, email, text message, and EDI. Since 1992, Retarus has stood for technically advanced fax communications for businesses. Incorporate our expertise in fax transmission in your software today. Easy. Fast. And reliable.

Retarus Enterprise Fax-APIs:
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