/etc/postfix/main.cf

Configure the Postfix MTA to support SASL

smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = no
smtpd_sasl_exceptions_networks =
smtpd_sasl_local_domain =
smtpd_sasl_path = smtpd
smtpd_sasl_security_options = noanonymous
smtpd_sasl_tls_security_options = noanonymous
smtpd_sasl_type = cyrus

/etc/postfix/master.cf

Disable the run of the Postfix MTA in a chroot environment

smtp inet n - n - - smtpd

/etc/postfix/sasl/smtpd.conf

Tell Postfix where he finds the saselauthd socket file

pwcheck_method: saslauthd
saslauthd_path: /var/run/saslauthd/mux
mech_list: PLAIN LOGIN

/etc/pam.d/smtp

Configure PAM to support local unix Authentication for the SMTP Deamon

auth required pam_unix.so
account required pam_unix.so
password required pam_unix.so
session required pam_unix.so

Finally be sure saslauthd is running and is pointing to the right directory

/usr/sbin/saslauthd -a pam -c -m /var/run/saslauthd -n 5

Here a Python Script to Test the Auth

#!/usr/bin/python
 
import argparse
import smtplib
 
if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Tests SASL')
    parser.add_argument('--username', '-u', dest='username', action='store', help='Username')
    parser.add_argument('--password', '-p', dest='password', action='store', help='Password')
    parser.add_argument('--host', '-H', dest='host', action='store', help='SMTP Hostname')
    parser.add_argument('--port', '-P', dest='port', action='store', help='SMTP Port', default='25')
 
    args = parser.parse_args()
 
    server = smtplib.SMTP(args.host, int(args.port))
    server.set_debuglevel(1)
    server.ehlo()
    server.starttls()
    server.ehlo()
    server.login(args.username, args.password)
    server.quit()
 
    exit(0)