The "Smtpd error sleep time" option specifies the time in seconds the SMTP server waits before sending a 4xx or 5xx SMTP server error response. This prevents naive clients from going into an error - disconnect - connect - error loop. This option sets the "smtpd_error_sleep_time" postfix variable.
The "Smtpd soft error limit" option specifies an error count lower limit. When an SMTP client has made this number of errors within a session, the server waits error_count seconds before responding to any client request. This option sets the "smtpd_soft_error_limit" postfix variable.
The "Smtpd hard error limit" option specifies an error count upper limit. The SMTP server disconnects after an SMTP client makes this number of errors within a session. This option sets the "smtpd_hard_error_limit" postfix variable.
The "Smtpd helo required" option optionally turns on the requirement that SMTP clients must introduce themselves at the beginning of an SMTP session. This option sets the "smtpd_helo_required" postfix variable.