Pop3 user could not send the mail to external mail

Hi Admin

  i have to created the pop3 user in my domino server, and enable the ssl port for the pop3 user, we are using the external  smtp server

whenever the pop3 user send the mail to external internet domain the following error showing

SMTP Server Attempt to relay mail to suer@gmail.com rejected for policy reasons. Relays to recipient’s domain denied in your configuration.