email a friend error

Greetings...

Has anyone have this error when the E-maila Frined form from the product is use? . NopCommerce is able to send notification and other email, however the Email a friend from not

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The following recipient(s) could not be reached:

real email@real domain.com

  Error Type: SMTP
  Remote server (xxx.xxx.xx.x) issued an error.
  hMailServer sent: .
  Remote server replied: 550 5.7.1 Requested action not taken: message refused