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.

All Documents and Formats

Send and receive all conventional Microsoft Office documents and image formats such as JPG, PNG, and BMP, as well as HTML, PDF, and TIFF files.


Scalable and Flexible

Prevent over- and under-utilization of capacity. With the Retarus IT infrastructure, you can send 1,000 messages today and 1,000,000 tomorrow.

Pay-Per-Use Billing

Experience transparency in billing too. Retarus enterprise fax APIs are billed as needed. According to set per-page pricing, irrespective of the duration of transmission.

Global and Available Anytime

Rely on global availability of reliable transmission. With our own data centers in Europe, Asia, and the USA, we offer maximum international availability. 24/7.

Enterprise-Level SLAs

Choose a service level agreement that meets your needs in terms of quality and response time.

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.

Even more benefits for you …

Never Busy Technology

Lower the failure rate of fax transmission by up to 10% This Retarus technology ensures that multiple fax jobs are never sent to one recipient simultaneously, meaning they can’t block each other from being received.

Telephone Number Service

Receive faxes anywhere. Retarus can provide you with your own incoming fax numbers on any continent and port your existing telephone numbers.

OCR and Barcode Recognition

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

Security and Compliance

Rely on Retarus’ global data centers. They comply with the most stringent data protection and data security requirements, including HIPAA and PCI DSS.

Long-Term Archiving

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

PGP and X.509 Encryption

Increase your security when transmitting faxes. Retarus enterprise fax APIs offer encryption for both incoming and outgoing faxes.

Transparent Billing

Count on maximum billing transparency. We bill according to client or cost center upon request.

Monitoring and Analysis

Monitor the success of your fax transmissions. In real time and over longer periods of time.

Service and Support

Experience first-class support. The Retarus Team is here to answer your questions and tailor your enterprise fax API 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.
View use case

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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