I have a few clients who have on-premises Exchange Servers. They need a superior anti-spam solution to what they have right now.
Many of them like the idea of Office 365, and the idea of Office 365 handling the sending/receiving of email on their behalf is appealing, but they don't want to use the whole service. They made an investment into on-premises exchange server and want to keep using that.
The Office 365 EOP
plan looks like it fits the bill.
My main question is... does EOP handle both the sending AND receiving of the company mail? Essentially acting as a gateway between the corporate Exchange Servers and the outside world? Or is it only for santizing the inbound mail and the organization is left up to their own devices to figure out how to send outbound mail?
Secondly... it's licensed on a per-user basis. How do you keep track of the users in Exchange vs the users in Office 365? Are you billed on a per-email-address basis? Or do you have to sync the AD users with Office 365? Does this mean there's an additional step every time you create a new user in AD that you must go into Office 365 and add an account there as well?
Lastly.... can you do exactly this but with E1 licenses instead of EOP licenses? Basically don't use any of the extra features of the E1 license, just use Exchange Online Protection but have all the users licensed with E1 licenses instead of the EOP licenses?