Postfix + SASL (Dovecot)

Dovecot - conf.d/10-master.conf

service auth {
...
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    # Assuming the default Postfix user and group
    user = postfix
    group = postfix        
  }
  ...
}

# Outlook Express and Windows Mail works only with LOGIN mechanism, not the standard PLAIN:
auth_mechanisms = plain login

Postfix - main.cf

smtpd_sasl_type = dovecot

# Can be an absolute path, or relative to $queue_directory
# Debian/Ubuntu users: Postfix is setup by default to run chrooted, so it is best to leave it as-is below
smtpd_sasl_path = private/auth

# On Debian Wheezy path must be relative and queue_directory defined
#queue_directory = /var/spool/postfix

# and the common settings to enable SASL:
smtpd_sasl_auth_enable = yes
# With Postfix version before 2.10, use smtpd_recipient_restrictions
smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination