Thanks guys! The problem is occurring prior to squirrelmail. Login over telnet fails as well.
telnet localhost 143
Trying ::1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN] Dovecot ready.
a login mtnman@awaycamping.com password
a NO [AUTHENTICATIONFAILED] Authentication failed.
Then in the mail log:
Feb 9 02:58:24 dovecot: imap-login: Disconnected: Inactivity (auth failed, 1 attempts): user=<mtnman@awaycamping.com>, method=PLAIN, rip=::1, lip=::1, secured
This is in the mail log when trying to login with squirrelmail:
Feb 9 02:57:55 postfix/smtpd[21547]: warning: SASL: Connect to private/auth failed: Permission denied
Feb 9 02:57:55 postfix/smtpd[21547]: fatal: no SASL authentication mechanisms
Feb 9 02:57:56 postfix/master[18521]: warning: process /usr/libexec/postfix/smtpd pid 21547 exit status 1
Feb 9 02:57:56 postfix/master[18521]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling
Is any of this of value for diagnostics?