Resolution

If you set Parallels Plesk Panel (PPP) server as outgoing SMTP server in mail account preferences of your mail client, try to send a message to some external recipient through this mail server and get this error, it means that the server requires authorization and you did not authorize before sending. Make sure that SMTP authorization support is enabled in your mail client preferences. For example in Outlook check authorization properties in Tools > Accounts > Mail > Mail Account > Properties > Servers > Outgoing Mail Server > Settings. There should be checkbox 'server requires authorization'. Use full mail name for authorization, for example 'name@domain.com' but not just 'name'.


If POP3 authorization is enabled in PPP, then you may authorize with POP3 (simply check for new mail) to the server first, then you will be able to send mail within "POP3 lock time" that is set at Server > Mail page in Plesk Control Panel.

If you get the bounce message with such error when send mail to a domain hosted on the Parallels Plesk Panel server, then make sure that the Mail service for this domain is enabled and the domain name is listed in $QMAIL_ROOT_D/control/virtualdomains and $QMAIL_ROOT_D/control/rcpthosts files.
If not, use $PRODUCT_ROOT_D/admin/sbin/mchk utility to rebuild Qmail configuration.