Arne Berglund put forth on 9/14/2010 1:42 PM:
Well, something doesn't seem right, then. I've got 0.4-stable in production now (apache on linux) connecting to a separate IMAP server (dovecot on linux as well). Granted, both boxes are in the same rack and on 1000BaseT ports on the same switch, but it's still having to go box-to-box for everything. I don't even have caching enabled, and things seem to work reasonably fast.
Caching isn't required for good performance when you have a 100 MB/s pipe with sub 1 ms latency between the RC and IMAP servers. If the average broadband connection is DSL/cable at 2 Mb/s that's a 500x difference in B/W.
If you were to locate your RC server across town on a DSL/cable line your RC performance would drop considerably due to that 500x decrease in bandwidth and latency increase of over 30x. In this scenario, RC caching and imapproxy would help quite a bit.