Exchange 2013 IMAP and POP Backend Services
Microsoft has made changes in Exchange 2013 for how IMAP and POP communicate between the Exchange servers holding the Client Access and Mailbox role. The roles below need the following services started for the Exchange servers to communicate properly with IMAP and POP.
Client Access Role: The following services need to be started for each server holding the CAS role to accept the connection from clients.
Mailbox Role: The following services need to be started for each server holding the Mailbox role to accept the connection from the CAS.
On servers where the Client Access and Mailbox roles are running on the same server, you manage both services on the same computer.