Enable imap(s) / pop(s) proxy in carbonio

Hello everybody,
I need some documentation or info about the subject.

I have migrated a test domain from a zimbra 8 server (SRV1) to carbonio (SRV2).
Now i need to keep the user login to SRV1 when connecting with the mail client, but transparently being rerouted to SRV2 to download mail with imap or pop.

How can I accomplish this, at least the part related to carbonio ?

Thanks for your help.