Postfix 5xx Reject relay denied
I've noticed the last few days this number going from around 30-75 for "5xx Reject relay denied 100%", which is higher than normal. I'm not sure what it really means specifically and was hoping someone could shed some light on it.
An examlpe detail line for this is:
3 18.104.22.168 mail.ihara.com.vn 3 email@example.com