Exchange 2007 has been splited based on Server Roles so if you require any specific function on a server then it can be placed on indivudial server based on your requirement, Exchange architecture, performance, management or your organization's policies.
We used to set Front-End and Back-End server roles in Exchange 2003 but Exchange 2007 introduces five roles for an Exchange organization.
- Mailbox
- Hub Transport
- Edge Transport
- Client Access
- Unified Messaging
Brief overview of each roles are below.
1. Mailbox Server
- Use for holding all Exchange Database - Mailbox & Public Folder (optional).
- It should be part of Domain & AD.
- 50 Storage Groups & 50 Mailbox Stores in each Storage Groups.
- STM File architecture has been removed.
- Proper backup recovery plans should be in place for High Availability.
2. Hub Transport Server
- Responsible for internal mail flow. (Same like Bridgehead in Exchange 2003).
- It should be part of Domain & AD.
- Incoming Mail Flow : Mailbox <- Hub Transport <- Edge Transport <- Internet.
- Outgoing Mail Flow : Mailbox -> Hub Transport -> Edge Transport -> Internet.
- Hub Transport can be placed instead of Edge Transport and can act for the similar function.
- Transport Agents, AntiSpam, AntiVirus can be enabled.
- Disclaimer can be set on.
- One Hub Transport role should be placed at a AD Site for good architecture.
3. Edge Transport Server
- Should be placed in Edge of your organization ( in workgroup / DMZ / perimeter ).
- Should NOT be a member of Domain & AD.
- ADAM ( Active Directory Application Mode ) provides AD information to Edge Transport server with help of Exchange component "EdgeSynch" by creating one way synchronization (from Domain to Edge Server).
- ADAM & EdgeSynch provides AD recipient information & SPAM filtering efficiency.
- Provides better Anti-spam and Anti-virus protection with help of connection filtering, content filtering, recipient filtering, SenderID, sender and IP reputation.
- Edge Transport Rules to protect Exchange environment, based on SMTP and MIME addresses, words in the subject and message body, and SCL rating.
- Address rewriting feature allows to modify the SMTP address on in/out-bound mail.
- Client Access Server was known as a Front End in Exchange 2003.
- It should be part of Domain & AD.
- Handles all the milbox access request comes from
- Outlook Anywhere - Application (like Outlook 2003 or 2007).
- MAPI, POP3 or IMAP4 client - like Outlook Express and Eudora
- Exchange ActiveSync - Mobile devices ( like Windows Mobile 5 Smartphone, pocket PC or any other device).
- Outlook Web Access (OWA) including Sharepoint & UNC access.
- Clietn Access provides Autodiscover mailbox location for Microsoft Outlook 2007.
5. Unified Messaging
- Merge VoIP environment with Exchange.
- Requires VoIP Gateways or PBXes to connect with Exchange.
- Access Voice Mails by using OWA.
- Outlook Voice Access provides below things.
- Listen voicemails.
- Forward or reply to messages.
- Get emails automatically & read via text-to-speech interface.
- Get calendar information.
- Accept or reply to meetings.
- Set voicemail Out-of-Office messages.
- Access or dial contact.
- Reconfigure the lite settings on the mailbox.