Emails from Yahoo accounts are blocked by the Email Security appliance with Greylisting Enabled
12/20/2019 1035 11150
DESCRIPTION: Emails from Yahoo Accounts are getting blocked by the Email Security Appliance with Greylisting Enabled.
This is due to Yahoo not re-attempting to resend the email, and so the Greylisting function won't let the mail through as it waits for the next connection attempt before allowing the mail through.
You can either temporarily disable the Greylisting and let the mail go through, then re-enable the Greylisting to populate the ES whitelist with the connecting IP, or review the email headers and add the Yahoo mail server connecting IP to the Whitelist, under Connection Management > Manually Edit IP Address Lists > Edit Allowed List.