What does "user $to unknown on host $smtp" mean in Perl's Mail::Sender?

Question

I'm using Mail::Sender to send mail from Perl. I have a valid SMTP server (it works if I do a telnet). However, I get an error -6 on a MailMsg. The doc shows -6 as

local user $to unknown on host $smtp

What does this mean? Is it unable to locate the receiver?

my $rec=(new Mail::Sender)->MailMsg(
    {smtp=>'smtp.example.net',
     from =>'[email protected]', 
     to => '[email protected]', 
     msg => 'Hello'});

Answer 1

If you see the AUTHENTICATION part of the documentation of Mail::Sender, it states that:

If you get a "Local user "[email protected]" unknown on host "zzz"" message it usualy means that your mail server is set up to forbid mail relay. That is it only accepts messages to or from a local user. If you need to be able to send a message with both the sender's and recipient's address remote, you need to somehow authenticate to the server. You may need the help of the mail server's administrator to find out what username and password and/or what authentication protocol are you supposed to use.