postfix ne marche pas ?

[Tom.]

j'ai un mail genre mail@mondomaine.com

et voici mon cat /etc/passwd:
theonegri:/# cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
sshd:x:100:65534::/var/run/sshd:/usr/sbin/nologin
Debian-exim:x:101:103::/var/spool/exim4:/bin/false
bind:x:102:104::/var/cache/bind:/bin/false
mysql:x:103:105:MySQL Server,,,:/var/lib/mysql:/bin/false
postfix:x:104:107::/var/spool/postfix:/bin/false
polw:x:105:109:policy-weight user,,,:/var/lib/polw:/bin/false
postgrey:x:106:110::/var/lib/postgrey:/bin/false
proftpd:x:107:65534::/var/run/proftpd:/bin/false
ftp:x:108:65534::/home/ftp:/bin/false
vmail:x:1000:8:vmail-user:/home/vmail:/bin/false
vu2000:x:2000:2000:vu-master:/var/www/fcgi/master:/bin/false
vu2001:x:2001:2001:virtual-user:/var/www/virtual/theonegri.com:/bin/false

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Ceci dit, qund je tente d'envoyer un mail a root@mondomaine.com ou abuse@mondomaine.com (des mails que j'ai cree), le resultat est le meme. Unknow user root ou abuse.