Since upgrading to 4.5.9 we are experiencing false positive spam scores on email messages originating from outlook clients and addressed to addresses on our local (internal domain). The users have been added since the upgrade, and are not using the Zimbra Connector.
The fix has been adding our local domain to the
/opt/zimbra/conf/salocal.cf.in -- the entry is whitelist_from *@ernesthealth.com
run zmcontrol stop and then zmcontrol start following your edits.