In my last post, I discussed a mail-flow scenario where you host some mailboxes on premises and some in the cloud (with Office 365/Exchange Online). In this post I want to point you to a couple resources if you are a Forefront Online Protection for Exchange (FOPE) customer who is thinking about moving a subset of your mailboxes to the cloud and you want to continue FOPE protection for your on-premises mailboxes.
Moving FOPE-Protected Mailboxes from On Premises to the Cloud discusses the high-level steps involved for you, as an existing FOPE customer, to begin the transition process to cloud mailboxes and continue FOPE protection for all users. Shared Address Space with On-Premises Relay Scenario (MX Points to FOPE) goes into detail concerning the configuration settings necessary (for FOPE, Exchange, and Exchange Online) for making this transition work.
I hope you find these helpful as your set up your cross-premises mail flow.