I am in the process of testing out Zimbra now and plan to start migrating users to it once I am comfortable with the stability. I currently use sendmail and have 3 Linux sendmail servers, each located at our largest facilities. I just want to run my planned config by everyone to ensure we set it up properly.

We have the following locations:
Co-location facility - no employees, but it is where I plan to install 2 servers, 5MB connection to the Internet. All Zimbra clients will come through this connection if they are accessing from any Internet connection.
Primary facility - about 100 employees, 25 will be on zcs connector with Outlook and 75 will run with Zimbra web client - T1 to the Internet
Warehouse - 2 to 5 users using Zimbra web client - 144K DSL Internet connection
Sales office - 2 users using Zimbra web client - 144K DSL Internet connection
Warehouse, 30 users mostly using web client- 768K to the Internet
Sales office - 3 users using Zimbra web client - 600K DSL connection
Warehouse - 4 users using Zimbra web client - 144K DSL connection
Warehouse - 40 users mostly using Zimbra web client - 768K Internet connection
Warehouse - 20 users mostly using Zimbra web client - Cable Internet connection
Sales office - 3 users using Zimbra client - cable Internet access

Also, 140 field sales reps with laptops will be accessing their mail from Outlook Express clients and a small amount of web client access. What are my options to connect these Outllok Express users? Can we use IMAP? Is our only option POP? I want to know the best way to handle these users because the web client is not a good only option. I also don't want to purchase Outlook Express for all of them.

Does the client access sound feasible? My main concerns are bandwidth usage and functionality for web client users and using Outlook Express for lower end laptop users. I know I lose some functionality with Outlook Express, but I need to use it for all laptop users that aren't Executives. Execs and Directors will get Outlook 2003.

In regards to the server, if I setup 2 servers, what are my options? Can they be load balanced? Should I setup one server at our primary facility and one at the co-lo? I would like to have some sort of server redundancy, but want to know how I should configure them.