Exchange 2003 Front /Back end

Any expert out there to explain why Microsoft came up with Exchange Front/Back end servers.?
I believe even without Exchange Front end , mobile users still can use OWA to access their mailboxes.

Is it a factor of security? most of the envuronments don't put the FE in the DMZ, they just put it in the same LAN as the Back end.
Do internet emails like Yahoo, Hotmail go through FE to get the message to exchange server?

Many Thanks
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tigermattConnect With a Mentor Commented:

Typically the Front End is used when you have multiple mailbox servers. It allows incoming access to OWA, RPC over HTTPS or ActiveSync to be proxied to the proper back-end mailbox server.

If you don't have a front-end server, you would have to expose every single Mailbox Server to the Internet on its own public IP address and DNS name, because one back-end server cannot proxy requests to other back-end servers.

With a single mailbox server it is pointless installing a front-end server. It is a waste of licensing, hardware and the energy bill to run / cool it. It gives you no security or performance benefit in this scenario.

Incoming email from the Internet and outgoing email would also typically pass through the front-end servers which then delivers it to the mailbox on the appropriate back-end server.

Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
To sell more Licenses!!!

But it it's security, but it does get expensive if you do it correctly, because if you use Load Balanced Front End Servers, you also need TWO (2).

and also Microsoft ISA/Forefront, because you don't really want to open up all the ports from DMZ to internal LAN for AD to work as well! Because your front end servers also have to be in AD.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
As you Yahoo and Hotmail, they are using different systems.

But they will have dediciated SMTP Servers, Anti-Virus, Anti-SPAM, appliances, before the email reaches the back-end mailboxes in their secure internal LAN.

What we "see" is a secure front-end which has access to proxyied - back end servers via firewalls to back end servers containing all the mailboxes (and the mailboxes will be on multipe cloud based platforms and grid servers).
jskfanAuthor Commented:
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