IMAP proxy recommendations.

[sofkam]

I am in the process of replacing our Cyrus Front-End servers with a 
proxy server that can front both Exchange and Cyrus IMAP, as well as 
future IMAP hosts as we move and migrate users.  The two that stand out 
are:  Perdition, and NGinX.  I'm looking for recommendations, or 
experience with either, or additional suggestions to examine.

Initially it will replace the old (and back-leveled) Cyrus Front-End 
servers in our murder aggregate, and I would like that process to be 
smooth and transparent.  But the proxy will then be switching back-ends 
based on Exchange vs Cyrus hosted IMAP  (Currently Exchange users are 
told to configure their clients with a different server, a practice we 
would like to discontinue.)  We will also be migrating users (usually 
from Cyrus to Exchange, but the other direction happens as well), and we 
would like this process to be as transparent as possible.   Finally, our 
Webmail server will also be using the proxy, so a proxy that maintains 
state-full connections would be a plus, but this takes second place to 
location transparency.

Because of the need to host multiple back-ends based on account, I have 
not so far been considering imapproxy, even though this provides the 
state-full connections.

Any thoughts or suggestions welcome.

Thank You,
Mike

-- 
Michael D. Sofka               sofkam at rpi.edu
C&MT Sr. Systems Programmer,   Email, TeX, Epistemology
Rensselaer Polytechnic Institute, Troy, NY.  
http://www.rpi.edu/~sofkam/