Hi,
from your description it seems that the email has been marked as a spam because of it's content ("Rule system classified mail as SPAM"), despite the fact that it came from a trusted source ("IP (209.85.208.175) isn't found on cloud black list").
Ad. "Any ideas why this software is blocking trusted email?":
In order to answer this, please open a ticket with our support and provide them with sample(s) of mis-classified email(s).
Ad. "Does this software not send a quarantine report to end users?":
Yes it can, please refer here (https://help.eset.com/emsx/7.1/en-US/idh_scheduler_task_qreports.html).
Matej
JPVG gave kudos to M.K. in ESET Mail Security blocking GMail??
