[Dovecot] making IMAP quicker on LAN

Hi all,

I keep on hitting this problem when migrating new clients from POP or local IMAP servers (hosted on their LAN's) to my Dovecot setup, which is hosted properly in a data center. People usually complain that it's slower and although they're getting a kick ass mail setup it doesn't look good from their point of view.

I'm wondering if there is anything I could do to speed it up on their LAN's. What I mean is probably a caching IMAP proxy or some sort of replication to a local Dovecot server. Is this something Dovecot can do? I'd be really grateful for any opinions on how to tackle this problem.

Many thanks,

Andrew.