Which InterFAX API to use for sending faxes

InterFAX offers its clients several APIs that allow the client to interact with the InterFAX system for sending faxes. The APIs offered are REST (read more), SOAP (read more) and SMTP (read more). InterFAX also offers PCI compliant APIs for REST (read more) and SOAP (read more)

In this document, we will not discuss the merits of each API and when to use it from a programming perspective (you can find many discussions on this topic online), but rather compare the API and their offerings with the InterFAX system.

API choice of interfaces and security

Regular (non-PCI-compliant) + + +
PCI-compliant + + x

Compare API functionality

Easy to integrate into existing systems? Depends. The answer here depends on the type of application you are integrating InterFAX into. If this is a third-party application, the integration may be more difficult. If this a custom application which was developed in-house, the integration may be easier. Yes. The majority of existing systems already have the capability to send out emails which is all you will need to have in order to use the InterFAX SMTP interface.
Allows asynchronous file upload Yes Yes No No No
Allows for polling for fax status Yes. Polling the status of the fax is possible through the API. No.
Feedback for an outbound fax is sent by email back to the sender once processing of the fax is completed.
Delivery confirmation of fax message to InterFAX system Yes. Upon submitting the fax to the InterFAX system, the application will receive a response with the status of the fax submission. No. The sender does not know whether the email has reached InterFAX (unless manually checking the InterFAX portal)
Supports secure delivery to InterFAX? Yes, with SSL connection. Very easy to use SSL connection to support secure delivery from application to server. SSL is enforced. Yes, with email encryption. However, setting up email encryption is not trivial and not all mail systems support it
PCI-DSS compliant? No No Yes Yes No
Suitable for high volume faxing? Yes Yes No No No
Number of recipients per fax message* 20,000 20,000 1 1 500

(*) Read more about our system limitations

The general rule of thumb in selecting between the non-PCI and PCI versions of the API is – if you are sending content which includes credit card data or contains highly secure information, you should use the PCI compliant endpoint.

To summarize, if you are integrating InterFAX into an existing, legacy system where it is not possible to integrate our API, we recommend you use the SMTP interface. For all other scenarios, we recommend you integrate using our libraries (read more). Alternatively, you can integrate the API of your choice directly into your code – you can find the documentation for the APIs here.