EOP not Moving Messages to Junk Email On-Premises
Exchange Online Protection (EOP) is Microsoft's solution for anti-spam and anti-malware. It is included as part of Office 365/Exchange Online and you can subscribe to it for on-premises Exchange. When you implement EOP, you configure the MX records for your domain to deliver messages to EOP, and then EOP forwards to your Exchange server. If a message contains mailware or is obvious spam, it is typically blocked and not forwarded to your Exchange server. It can be quarantined in EOP or discarded. Where is gets a bit tricky is the messages that might or might not be spam. They're spammy, but might be legitimate email. In Office 365, those messages are automatically moved to your Junk Email folder. For spammy messages to be moved to your Junk Email folder in on-premises Exchange, you need to create a couple of transport rules. EOP adds an X-Forefront-Antispam-Report header to messages after they are evaluated. You need to create transport rules in your on-premises Exchange to read...