Unsuccessful Authentication avec Postfix

Bonjour,

Nous venons de commander une offre Exchange chez OVH. On arrive très bien à utiliser les compte via un client mail type thundermail mais avec postfix l'authentification echoue systématiquement.

Voici la configuration main.cf utilisée :

# See /usr/share/postfix/main.cf.dist for a commented, more complete version


# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = mail.domain.info
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = mail.domain.fr, localhost, localhost.localdomain, localhost
#relayhost = [ssl0.ovh.net]:587
relayhost = [ex4.mail.ovh.net]:587
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all

## Sasl

smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_passwd
smtp_sasl_security_options = noanonymous

le fichier sasl_passwd.db est bien généré et le mapping est correct dans /etc/postfix/sasl/sasl_passwd.

Par ailleurs la même config fonctionne parfaitement avec les boites de MX plan que l'on a sur d'autres domaines. (avec les server ssl0...)