[ubuntu] unattended upgrades - changing machine name in mail in subject mail

Hi

I need help.
I installed and configured unattended upgrades on vm machine where previously I have made so many changes in postfix that I couldn't send any mail. Now I copy settings from machine where postfix work. I repaired postfix and gets mails.
I changed mails from in unattended upgrades and that is work.

The problem is in mail on position named subject of mail. I get mails with subject contains name of machine witch do not correspond with computer name.

I found in files the procedure of getting subject.

Where can I change the machine name in this subject ?