Microsoft exchange Server Scenario

["lists" <lists () brianburns net>]

Forgive me if this has recently been brought up. I need some best practice information for the following scenario using 
Microsoft Exchange Server:

I have several thousand users on Exchange Server. Approx half of these users need to access their mailbox from the 
protected LAN/WAN segments as native MS Exchange clients using Outlook.  The exchange servers are members member of the 
internal NT domain. The admin group only wants to create a single account for each mail user, and not have to maintain 
seperate directories (based on the outcome of these questions, this may be able to change)

The other half of my users need to access their mail accounts from the internet via standard POP3/SMTP protocols. A VPN 
is not logistically feasable for this purpose.

I am using Checkpoint FW-1 with a DMZ.

How should I architect my mail infrastructure and still maintain some semblance of security? Any 
advice/criticicism/help would be very much appreciated.

Thanks,

Brian Burns
mailto:brian () brianburns net