Pb de resolution inverse

Bonjour tout le monde,

Mon probleme est le suivant. Apres configuration de mon server smtp sous postfix (qui tourne sous linux Fedora Core 4). La plupart des mails transitant par ce server arrivent a etre relayer correctement vers leur destinataires mais les mails a destination de cetains domaine comme ifrance.com et un autre , n'arrivent pas a etre delivrer car le server mail du domaine du domaine distant (comme ifrance par ex. )refuse le relayage du courrier et je peux lire au niveau de mes fichier log ce qui suit:
Feb 19 04:13:42 smtp postfix/qmgr[7728]: 6A9A73009DC: to=<maxreel@ifrance.com>, relay=none, delay=410972, status=deferred (delivery temporarily suspended: connect to mailrecv.ifrance.com[82.196.5.134]: server refused to talk to me: 450 Client host rejected: cannot find your hostname, [81.91.238.239] )
Quelqu'un pourrait il m'aider a resoudre ce probleme. Ci dessous ma config du server smtp (postfix):
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
home_mailbox = Maildir/
html_directory = no
inet_interfaces = all
local_recipient_maps =
mail_owner = postfix
mailbox_command = /usr/bin/procmail
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = mail.$mydomain,$myhostname,localhost.$mydomain,localhost
mydomain = otitelecom.bj
myhostname = smtp.otitelecom.bj
mynetworks = /etc/postfix/mynetworks
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.2.2/README_FILES
relay_domains = $mydestination
sample_directory = /usr/share/doc/postfix-2.2.2/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
unknown_local_recipient_reject_code = 550

Merci d'avance

Christian