In the following situation we will configure :

If we deploy an Exchange Server in organization with multiple forests, we must install Exchange Server in each forest and then connect the forests using appropriate cross-forest trusts. The trust allows users to see address and availability data across the forests.

In an Exchange Server 2013 organization, if we want direct mail flow between Exchange servers in different forests, we must configure SMTP send connectors and SMTP receive connectors on the Mailbox servers that should communicate directly with each other.

Mailbox Server,Client Access Server,Legacy Edge Transport Server,Unified Messaging service,Transport service.

In Exchange Server 2007, we need a dedicated hardware for clustered Mailbox servers, and we cannot run other roles, and failover occurred at the server level in that server.

But in the latest versions of exchange servers we do not need dedicated clustering hardware for highly available Mailbox servers. It will manage automatically by exchange server windows components.

No need to use Local Continuous Replication (LCR), Cluster Continuous Replication (CCR), or Standby Continuous Replication (SCR). LCR has been discontinued. Key features of CCR and SCR have been combined, enhanced, and made available through database availability groups.

we can combine Exchange roles on highly available Mailbox servers, that is providing no need to use windows network load balancing. This means we can create a fully redundant Exchange organization using only two Exchange servers. In this case, each server would have the Mailbox and Client Access roles. You would also need a witness server for the database availability group, which doesn’t have to be an Exchange server.

Database names must be unique throughout your Exchange organization. This means you cannot name two databases identically even if they are on two different Mailbox servers.

Every mailbox database, except copies, have a different globally unique identifier (GUID). Copies of a database have the same GUID.

Mailbox servers that are part of the same database availability group do not require cluster-managed shared storage. However, the full paths for all database copies must be identical on host Mailbox servers.

Exchange 2013 no longer has public folder databases. Instead, special mailboxes are now used to store the public folder hierarchy and content. Like traditional mailboxes, special mailboxes for public folders are stored in mailbox databases and are replicated as part of any database availability group you configure.

New-MailboxRepairRequest -Mailbox ExchangeID