I did some more testing:
:~# dig MX france-tracker.net
; <<>> DiG 9.3.2-P1 <<>> MX france-tracker.net
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18558
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;france-tracker.net. IN MX
;; AUTHORITY SECTION:
france-tracker.net. 3559 IN SOA ns1.domainpeople.com. root.domainpeople.com. 2001050903 28800 14400 3600000 3600
;; Query time: 3 msec
;; SERVER: 172.16.3.70#53(172.16.3.70)
;; WHEN: Sat Jan 20 17:08:53 2007
;; MSG SIZE rcvd: 97
Apparantly you have not set your DNS MX record. Thus, external sites do not know to which server / IP they have to connect to deliver mail.
To setup a MX record, go to your DNS manager in ISPConfig, click on your site, and go to the tab 'records'.
Scroll down till you see MX with a new button. I think there's no entry for MX, right? Click on the new
button, leave the hostname field empty and enter your system name (cip001.france-tracker.net) in the mailserver field. Press save.
Now this is DNS, so it may take a while before it is propagated all over the world. You can check this yourself. Mail should start to work by using the dig command above. You should see a line somewhere in the middle saying:
;; ANSWER SECTION:
france-tracker.net. 86400 IN MX 10 cip001.france-tracker.net.
Then start testing your email again.