How to send fax to sandbox account

• https://developer.ringcentral.com/api-docs/latest/index.html#!#RefFaxMessages.html

• PHP on Packagist: https://packagist.org/packages/ringcentral/ringcentral-php
• PHP on GitHub: https://github.com/ringcentral/ringcentral-php
• JavaScript on GitHub: https://github.com/ringcentral/ringcentral-js#fax
  

• Ruby fax docs: http://ringcentral-sdk-ruby.readthedocs.org/en/latest/usage/messages/Fax-Messages/
• Ruby SDK: https://rubygems.org/gems/ringcentral_sdk

The following reference also useful for a person who needs to know about fax in ringcentral and all about frequently asked questions:

https://forums.developers.ringcentral.com/questions/144/fax-faq.html

This is an important link and helpful for a person going to start using fax service and want to know everything about it