Unsuccessful connection to the IMAP server on 5 server freshly installed

you can not login in webmail , email logs do not show any kind of error, how can I solve?

Versione 1.1.0-rc4.3
build 20131017
Debian 7.0

postfix + roundcube + courier

i have try

# perl /var/www/imscp/engine/setup/set-engine-permissions.pl
# service courier-authdaemon restart

but without success

So for those who are into the same problem, Check well the DNS configuration of domains and domain of the server (admin.nomeserver.ext)