The key word here is 'relay.' The server cannot authenticate either your sending email id or the recipient id. I suggest you check your SMTP server setting to see if you have provided proper email address.

Thanks for your suggestions David, but my SMPT server settings are provided properly.

It's a complete mistery for my, I hope you, our someone else in this forum can help me out with this issue

Thanks in advance, P.Rensel

Many email providers are increasing security checks, so there may be something that needs to change in your settings. Possibly, if you post a screenshot of your SMTP settings, someone here may have suggestions.