Postfix host has a lot of 'CLOSE_WAIT' sessions on port 25

Issue

A lot of 'CLOSE_WAIT' connections to port 25 remains on postfix server.
Service monitoring software is connecting to the postfix server every 15 minutes and the network sessions remains with CLOSE_WAIT status.
Error message "fatal: open database /etc/postfix/access.db: No such file or directory" is logged to /var/log/maillog file when a client connects to SMTP port.

• /var/log/maillog

Jun 20 03:13:19 posthost postfix/smtpd[714]: fatal: open database /etc/postfix/access.db: No such file or directory
Jun 20 03:13:20 posthost postfix/master[3401]: warning: process /usr/libexec/postfix/smtpd pid 714 exit status 1
Jun 20 03:13:20 posthost postfix/master[3401]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling