Emails are sent but not delivered into partner inbox
Emails sent from Post Affiliate Pro are delivered only to some email servers, but not to all and are often marked as apam.
Check your email (SMTP) server logs, if you see log similar to this:
May 9 13:01:00 example postfix/smtp[12722]: 71F4110179: to=<support@qualityunit.com>, relay=qualityunit.com[50.28.21.67]:25, delay=2.3, delays=0.53/0.01/1.6/0.15, dsn=5.0.0, status=bounced (host qualityunit.com[50.28.21.67] said: 550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1) (in ...