The "Disable verify command" option allows you to disable the SMTP VRFY command. This stops some techniques used by spammers to harvest email addresses. This option sets the "Disable verify command" postfix variable.
The "Smtpd banner" option specifies the text that follows the 220 status code in the SMTP greeting banner. Some people like to see the mail version advertised. By default, Postfix shows no version.
You MUST specify the "$myhostname" at the start of the text. When the SMTP client sees its own hostname at the start of an SMTP greeting banner it will report a mailer loop. That's better than having a machine meltdown. This option sets the "smtpd_banner" postfix variable.
See the examples bellow:
Smtpd banner = $myhostname ESMTP $mail_name ($mail_version) Smtpd banner = $myhostname ESMTP $mail_name
The "Smtpd recipient limit" option restricts the number of recipients that the SMTP server accepts per message delivery.
The "Smtpd timeout" option limits the time in seconds to send an SMTP server response and to receive an SMTP client request.
Note: if you set SMTP timeouts to large values you must update the global "Ipc timeout" option as well. This option sets the "smtpd_recipient_limit" postfix variable.