For the Forgot Your Password link in the Sign In page or the Reset Password button in the Admin->User Account page to show up, a SMTP server is required to be set up in the System Settings. Any modification of the MongoDB user account passwords could compromise the security or integrity of you Alteryx Server environment.
I would check with your IT department to see if either gaining access to your company's SMTP server or installing a SMTP server (http://www.vsysad.com/2017/05/install-and-configure-smtp-server-on-windows-server-2016/) would be allowed, even if temporary, as it is needed for the Gallery with Built In Authentication to work completely. Please note that the SMTP connection can be configured with authentication and SSL.
@MattHthanks for the reply.
It was a client site that wasn't allowing the SMTP to be setup, but they have since done so.
Thanks
Dave