I could not send/receive ANY mail! When I tried to send an email from any ispconfig email address which all worked on the original server, it would return with an error. Like a postfix missmatch or something.
Are there any errors in your mail log?
Are your DNS records ok (MX, PTR, SPF)? Did you update them to the new IP?
I'm afraid I can't say much about the chroot problem - it's a long time since I have used it...