Sending Fax Limitation

The older FaxOut API: https://service.ringcentral.com/faxoutapi/ has a limit of 49 recipients. Once you hit 50 you'll need to use the FaxResource per this documentation: http://success.ringcentral.com/articles/en_US/RC_Knowledge_Article/6643

OR

The newer Connect Platform API's Message resource for Fax: https://developers.ringcentral.com/api-docs/latest/index.html#!#FaxMessages.html has the same limitations for recipient quantity, but expanded functionality beyond these limits.