Hi to all I have some *production* pop3/inappropriate server that i would like to move under a proxy

Some questions: this because I'll use local IPs on each mail server.

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.

3. Performance for the proxy server? The same as the mailserver or higher due to the missing email computation? In example, the proxy doesn't have to access disks or emails data but has only to transmit what the mailserver osd saying

4. Like question 3, any real users for the proxy? I would like to know some info about hardware and userbase (in example: dual quad xeon 5600, 32Gb ram, 10.000 concurrent sessions) In my case I'm planning for about 100 active sessions. Can i use a small EC2 instance?