There are no SenderID entries in maillog, indicating that outgoing antispam is not working:
~# grep -i SenderId /usr/local/psa/var/log/maillog
var/log/messages contains following errors:
Jul 8 11:42:50 server ctasd: Create ASAP Main object failed [SingleEngine] - Invalid LicenseKey
Jul 8 11:42:50 server ctasd: Init engines failed
Go to Home > Tools & Settings > License management > Additional License Keys
If "parallels-premium-outbound-antispam-unix" license key is in the list, select its checkbox and Press "Install key" . Otherwise, upload proper key and install it.
Restart outgoing antispam service:
~# /etc/init.d/ctasd_initd restart
License key was not installed/activated properly.