Comment 57 for bug 875440

The fix from Devin appears to have worked for me:

# cat /etc/postfix/sasl/smtpd.conf
pwcheck_method: saslauthd
mech_list: plain login cram-md5 digest-md5
log_level: 7
allow_plaintext: true
auxprop_plugin: sql
sql_engine: mysql
sql_hostnames: 127.0.0.1
sql_user: <user>
sql_passwd: <pass>
sql_database: <db>
sql_select: select crypt from users where id='%u@%r' and enabled = 1