2 servers 1 real mail server and 1 future zimbra mail server

[bunam]

So that is the situation :

I'v got a real mail server for dom1.com and dom2.com (with a valid mx, etc...)

I'm installing a new one with zimbra and preconfigurated with future dom1.com and dom2.com
When i do a dig dom1.com MX on the zimbra server it find the first as the best MXs cool !!
But when i send mail to toto@dom1.com from the zimbra server it deliver localy (with the shell command mail toto@dom1.com)

You have to know i have done a
cd /usr/sbin
and
mv sendmail sendmail.orig
and
ln -s /opt/zimbra/postfix-2.2.9/sbin/sendmail

Do you think it's correct that zimbra deliver localy the mails ??
It should'nt and send it to the best MXs ?

Also i have an other apache / php on the zimbra server that aparently coudn't send mails ;(

Thant's for your help