[nmglug] in house email server

[Andres Paglayan]

Hi,

I am trying to replace exchange,
not because I need, but because I can (or could with a little help)

IMAP is great for replacing the email backup and accessibility from  
wherever
and thanks to Jason, I found egroupware to be an excellent  
alternative for sharing calendars

does anybody have a good pointer or opinions on the following:

we use dreamhost for email and other stuff,
does it makes any sense to have an in-house email server for internal  
email?
how do you keep it simple for users, meaning to have only one imap  
account?
if using an in-house server, how do you address mobile users without  
opening the server to the public internet?

Thanks,