helo_name is not what i set

[Francesco Abeni]

Good morming everybody. Surely it is my fault, but i am not able to set 
 helo name as i want.

Here are relevant lines from postconf -n:
myhostname = srv04.givi.it
smtp_helo_name = smtp.givi.it
smtpd_banner = $smtp_helo_name ESMTP GIVI srl

I want helo name to be "smtp.givi.it", but it always appears as 
"srv04.givi.it". What am i doing wrong?

Thank you for any suggestion.

--
Francesco