PLPLUGA.E.MailSMTP(the error was the server rejected one or more recipient addresses)

Hi All

I setup an addin on a BIC report to email it to me after it runs, but I get the error: PLPLUGA.E.MailSMTP the error was {The server rejected one or more recipient addresses} The server response was {550 relay not permitted}

May I please get some guidance on what this error means and how to resolve it.