Previous versions of Microsoft Exchange employed traditional communication methods whereby email, voice mail, and fax traffic not only traveled different paths through communication networks (frequently requiring separate sites and servers), but were accessible only by different tools such as telephones, computers, and fax machines.
With Exchange Server, users receive e-mail, voice mail, fax messages, and calendar data directly into one inbox, and can access the inbox from a variety of applications, such as Microsoft Office Outlook, Outlook Web Access, mobile devices, or the telephone. This unified messaging system simplifies the user experience and reduces the number of servers required to provide e-mail, voice mail, and fax services.
Server roles provide flexibility in deploying Exchange Server. There are five server roles in Exchange Server:
Hub Transport server role moves messages between the other server roles and applies compliance policies to messages while they are in transit.
Client Access server role enables users to access their inbox from Outlook Web Access, POP3, IMAP 4, Outlook Anywhere, and Exchange Server ActiveSync.
Edge Transport server role provides antivirus and anti-spam protection for your Exchange organization.
Mailbox server role holds users’ mailbox databases, which contain e-mail, calendar, contact, task, voice mail, and fax data.
Unified Messaging server role lets users receive voice mail, e-mail, fax messages, and calendar data in their Exchange inboxes. It also enables voice access to the inbox from any telephone, and hosts any speech-enabled Automated Attendant that your organization may employ.
With the exception of the Edge Transport server role, which must be deployed on a server in the perimeter network, all other roles can run on one server or multiple servers, depending on the needs and size of your organization.
NOTE:
Exchange Server 2007 and 2010 have five server roles as describe above: Hub Transport, Client Access, Edge Transport, Mailbox, and Unified Messaging.
Exchange Server 2013 has only three server roles: Mailbox, Client Access, and Edge Transport. The Mailbox role includes Transport service, Mailbox databases, and Unified Messaging. The Client Access role provides authentication, limited redirection, and proxy services. The Edge Transport Server role provides improved anti-spam protection for your Exchange organization. It also applies policies to messages in transport between the organization. AppManager for Microsoft Exchange Server and Exchange Online discovers the Hub Transport and Unified Messaging roles under Mailbox role for Exchange Server 2013.
Exchange Server 2016 has two server roles: Mailbox and Edge Transport. The Mailbox role includes Transport service, Mailbox databases, Client Access service, and Unified Messaging. The Edge Transport role provides anti-spam and mail flow rules as mails enters and leaves your Exchange organization. AppManager for Microsoft Exchange Server and Exchange Online discovers the Mailbox databases and the Hub Transport, Client Access, and Unified Messaging services under Mailbox server for Exchange Server 2016.
Exchange Server 2019 has two server roles: Mailbox and Edge Transport. The Mailbox role includes Transport service, Mailbox databases, and Client Access service. The Edge Transport role provides anti-spam and mail flow rules as mails enters and leaves your Exchange organization. AppManager for Microsoft Exchange Server and Exchange Online discovers the Mailbox databases, Hub Transport, and Client Access under Mailbox server for Exchange Server 2019.