I have been looking to customize the MailServer SMTP Banner.(removing the Postfix name from the banner)
You can add or and customize as much as Postfix 2.x would accept it from this path:
I have edit the file main.template and add the following line:
smtpd_banner = $myhostname ESMTP
Saved and restart the SMTP component from the NAS web interface.
For DSM 5.1-5022 Update 4; The main.cf is located to :
If you need to reload Postfix; Run :