host not found

Hello,

I have Postfix installed on my server and it seems not having problems.
If I make 'postfix check' I receive no errors, but if I try to connect with
mail client I receive the message:

Connecting to SMTP server...
Host not found or network unreachable (TCP)

Someone can help me?

this is the result of postconf -n

>>>
alias_database = hash:/etc/postfix/aliases
alias_maps = hash:/etc/postfix/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
inet_interfaces = all
mail_spool_directory = /var/spool/mail
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, $mydomain
mydomain = fantacalcio2000.com
myhostname = mail.fantacalcio2000.com
mynetworks = 62.149.226.251/28, 127.0.0.0/8
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
readme_directory = /usr/share/doc/postfix-1.1.11/README_FILES
relayhost = $mydomain
sample_directory = /usr/share/doc/postfix-1.1.11/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
virtual_maps = hash:/etc/postfix/virtual
>>>

Thank you
Nicola