One of Our client (around 2000 user) keep telling me that they are facing performance issue for email solution. around 1000 people using IMAP configuration with ms outlook and around 700 - 1000 people using web interface as they are roaming users.

This client using MPLS ( 1 MBPS) as well as broadband ( 512 KBPS). When they use mails through MPLS in office performance is good...but through braodabnd is not good.
I know web interface ( AJX ) will take some time to communicate and its all depend upon the network connectivity.

1 ) i just want to know is their any suggestion i can give to customer for this ? i asked them to use standard html version for web interface to get better performance. ...any other suggestion ?

2 ) Is is the right decision to suggest user to configure their profile with IMAP? as i believe IMAP is online protocol and work differently than POP3 and it keep syncing with server...is it raise any issue with performance...??

Please suggest.