The system itself cannot send emails (e.g. by means of "Send Settings" button) because it open connection to port 25 and sends "EHLO localhost", instead of port 587 and a fqdn as a EHLO. Obviously:

Sep 26 08:37:44 mail3 postfix/smtpd[22477]: NOQUEUE: reject: RCPT from mail3[123.123.123.123]: 504 5.5.2 : Helo command rejected: need fully-qualified hostname; from=postmaster@domain.it to=test1@johndoe.com proto=ESMTP helo=

This happens because of "smtpd_recipient_restrictions" in postfix main.cf file:
"reject_non_fqdn_hostname"

Email should be sent through the submission port defined in master.cf

In application.ini I can read:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; See: http://framework.zend.com/manual/en/zend.mail.smtp-authentication.html
;;
;; Ensure you have a working mail server configuration so the system can
;; send emails:
;;
resources.mailer.smtphost = "mail3.domain.it"
;resources.mailer.username = ""
;resources.mailer.password = "96"
;resources.mailer.auth = ""
;resources.mailer.ssl = ""
resources.mailer.port = "587"

But it doesn't work…

What am I missing? What am I doing wrong?

TIA…