Comment 2 for bug 324736

I have also experienced this bug - the default installed configuration won't start with:

invoke-rc.d imapproxy start

which in turn causes the postinst script to bail out. It seems that the problem is the line:
server_hostname localhost

Since localhost likely is not an IMAP server. Maybe it would be good to provide an /etc/default file which prevents the proxy being launched by default until it is configured correctly.