Proxy IMAP/POP

[Luis Miguel Flores dos Santos]

Hello, I'm try configure dovecot to proxy imap and pop but I can't, follow my 
configurations:

dovecot version = 2.2.10

My configuration:

dovecot -n
# 2.2.10: /etc/dovecot/dovecot.conf
# OS: Linux 3.18.35 x86_64 CentOS Linux release 7.2.1511 (Core)
auth_mechanisms = plain login
auth_username_format = %n
disable_plaintext_auth = no
mail_location = maildir:~/Maildir
mbox_write_locks = fcntl
namespace inbox {
  inbox = yes
  location =
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix =
}
passdb {
  driver = pam
}
passdb {
  args = /etc/dovecot/dovecot-sql.conf.ext
  driver = sql
}
ssl = no
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem
userdb {
  driver = passwd
}
userdb {
  args = /etc/dovecot/dovecot-sql.conf.ext
  driver = sql
}

grep -v '^ *\(#.*\)\?$' dovecot-sql.conf

driver = mysql
connect = "host=127.0.0.1 dbname=mail user=root password=PASS"
password_query = SELECT NULL AS password, 'Y' as nopassword, host, destuser, 
'Y' AS proxy FROM proxy WHERE user = '%u'

/var/log/maillog:

RHDOVECOT dovecot: auth: Fatal: Unknown database driver 'mysql'


**OBS: I followed this wiki: 
http://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy
and installed dovecot-mysql.x86_64,
My server is a CentOS Linux release 7.2.1511 (Core)

Anyone can help me?

Thanks.


--------
Atenciosamente,

Luis Miguel