These configurations are part of a full-mobility solution for handling
email offline.  They assume that you have both a GMail account and a
corporate email account over a VPN.  Obviously you can adjust the
configuration based on your specific email providers.

Mutt is used for the email client, where you do your reading and
writing of email.  You can substitute a different email client, of 
course, but you need to configure the client yourself using the Mutt 
configuration here as a guide.

Offlineimap is used for synchronizing your local email store with the
remote providers, so you can read your email without a network

Postfix is used as a full-service mail transport agent (MTA) to
deliver your email to the remote systems when you're connected to the
appropriate network.  If you write email while offline, it will be
held (deferred) until you connect to the appropriate network again
using NetworkManager.  At that point the deferred mail for that
connection is delivered.

To read more about this solution, start here and follow the links:

PWF -- 2011-10-01