SMTP Error (550)

[todhend]

I realize this has been posted before but I can't find the fix
I have a fully functional subscription paid direct admin server on my network, it works fine, I'm trying to mimic the settings for Vesta, I have an external dns server and as far as I can tell everything is the same from the web portal set up, the only thing not working is sending mail, I immediately keep getting this error.
SMTP Error (550): Failed to set sender "USER" (Access denied - Invalid HELO name (See RFC2821 4.1.3)).

I have full access to the files of both servers, please guide me to the root of the problem

[todhend]

just found the issue, its working now

Here is the solution.

You should add smtp helo name in the configuration.

$config['smtp_helo_host'] = 'localhost';
Find the file config.inc.php from your mail client application, and add the line.

VestaCP: /etc/roundcubemail/config.inc.php