Weird "from" address in Postfix sent mails

Hello,

I just installed another WebMin+VirtualMin server on a Debian 5.0 x64 machine using the now famous "install.sh" :) Like my past experiences, smooth install !

My client just have a problem sending mail from his domains : the mail leaves the server but the "from" header is weird: "user.domain@localhost" instead of classical "user@domain.tld". So, if the destination host do a verification on the address, the message is bounced with this error : "550-Verification failed for <user.domain@localhost> / 550-Unrouteable address / 550 Sender verify failed (in reply to RCPT TO command)". If the destination host doesn't do verification, the mail is delivered.

I compared the configuration with another server I set up few month ago (but without this weird behavior) : identical.

So, I am here to ask for some advices. I tried one found on this forum ( http://www.virtualmin.com/node/11246) with no luck.

hostname : sd-XXXXX /etc/hosts :

127.0.0.1       localhost
88.191.73.169           sd-XXXXX
# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback

/etc/postfix/main.cf :

# 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 (Debian/GNU)
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.
 
myhostname = sd-XXXXX.dedibox.fr
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = localhost, sd-XXXXX.dedibox.fr, localhost.dedibox.fr, localhost
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_command = /usr/bin/procmail-wrapper -o -a $DOMAIN -d $LOGNAME
mailbox_size_limit = 0
recipient_delimiter = +
virtual_alias_maps = hash:/etc/postfix/virtual
sender_bcc_maps = hash:/etc/postfix/bcc
home_mailbox = Maildir/
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions = permit_mynetworks permit_sasl_authenticated reject_unauth_destination

Thanks for your help and your time,

Tristan