SMTP Authentication

Hello I use a 3rd party application (Gammadyne) to send bulk email to our customers. I am not asking for help with Gammadyne. When I attempt to send email, I am getting this error message. I have not seen this before. SMTP is turned on in cPanel and am using user Login credentials in Gammadyne for sending emails. >SMTP Error 4590: Server refused recipient kabernathy@XXXXXXXX.org: 550-Please turn on SMTP Authentication in your mail client. 550-static-47-206-223-127.tamp.fl.frontiernet.net (33helpme.com) 550-[47.206.223.127]:11430 is not permitted to relay through this server 550 without authentication. Thank you