[Dovecot] proxy configuration

[Ed W]

> Lessons learned?
> It works and it worked immediately. Store backend host information as IP
> address and not as host name.
>
>   

I have a setup similar to what the OP described.  The other missing 
ingredient is that in current stable version you need to change your 
mysql query to avoid returning any proxy results if the user somehow 
managed to end up on the correct backend server directly, ie you 
manually say that no proxying is required.  The point of the new feature 
that Timo added is then you can simply set IP addresses for each server 
and if the user happens to come in on the correct server already then 
proxying is automatically disabled (ie you can have a bunch of backend 
machines all pretending to be frontend machines and it all just works)

Ed W