Dovecot proxy

[Gandalf Corvotempesta]

2016-11-17 9:11 GMT+01:00 Gandalf Corvotempesta
<gandalf.corvotempesta at gmail.com>:
> Hi to all
> I have some *production* pop3/inappropriate server that i would like to move
> under a proxy
>
> Some questions:
> 1. Keeping the same original hostname on the proxy (in example
> mail.mydomain.tld)
> and changing the hostname on the imap server, makes some troubles like MUA
> redownloading all the messages?
> Is dovecot (running on the imap server) happy seeing the hostname change?
> What about maildirs, where the hostname is wrote on the mail file?
>
> 2. Dovecot proxy will proxy the whole pop3/imap traffic or only the login
> auth?
> I don't want to expose the mailservers to internet, all imap session must be
> proxied through the proxy.
> this because I'll use local IPs on each mail server.

Any advice on this, particurally on question 2 ?
The only way to get the real mailserver IP address is doing a
succesfull auth via proxy
or even in case of login failure the response is caming from the real
mail server ?