fatal: no SASL authentication mechanisms

[NaSa]

Hi every one
some error occur on postfix smtpd auth. and login to postfix always failed

maillog file

Code:

warning: SASL: Connect to private/auth failed: Resource temporarily unavailable
Oct 12 16:59:41 panel postfix/smtpd[26574]: fatal: no SASL authentication mechanisms
Oct 12 16:59:42 panel postfix/master[1116]: warning: process /usr/libexec/postfix/smtpd pid 26574 exit status 1
Oct 12 16:59:42 panel postfix/master[1116]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling
Oct 12 17:01:22 panel postfix/anvil[26491]: statistics: max connection rate 1/60s for (smtp:187.150.151.3) at Oct 12 20:58:07
Oct 12 17:01:22 panel postfix/anvil[26491]: statistics: max connection count 1 for (smtp:187.150.151.3) at Oct 12 20:58:07
Oct 12 17:01:22 panel postfix/anvil[26491]: statistics: max cache size 1 at Oct 12 20:58:07
Oct 12 17:03:05 panel postfix/smtpd[26913]: warning: 191.113.203.137: hostname 191-113-203-137.baf.movistar.cl verification failed: Name or service not known

i do not change any dovecot and postfix config files. and postfix mysql auth is ok!

any suggestion?