Are you using postfix?
Have you tried to restart it?
If you are using debian there is a package called postfix-mysql
try using
Code:
$ apt-get install postfix-mysql
but if you are using yum (fedora, centos), it is installed automatically when you install postfix.
and output of postconf -m looks like this in centos.
Code:
btree
cidr
environ
hash
ldap
mysql
nis
pcre
proxy
regexp
static
unix