Plesk Mail not working. Loogs show:

Dec 3 16:20:17 webserver postfix/cleanup[32266]: warning: connect to Milter service unix:/var/spool/postfix/ctmilter/ctmilter.sock: No such file or directory
Dec 3 16:20:17 webserver postfix/cleanup[32266]: A8D731406FD6: milter-reject: CONNECT from localhost[127.0.0.1]: 4.7.1 Service unavailable - try again later; from=<psaadm@webserver.domain.com> 

The Postfix config ‘/etc/postfix/main.cf’ contains entries with extra commas:

# grep milters /etc/postfix/main.cf    
smtpd_milters = ,, inet:127.0.0.1:12768 unix:/var/spool/postfix/ctmilter/ctmilter.sock   
non_smtpd_milters = ,, inet:127.0.0.1:12768 unix:/var/spool/postfix/ctmilter/ctmilter.sock   

smtpd_milters = ,, inet:127.0.0.1:12768

became

smtpd_milters = inet:127.0.0.1:12768

Then restart postfix,

# service postfix restart

Other sources:
http://kb.sp.parallels.com/en/121170
http://kb.sp.parallels.com/en/116748