I check what I had I my mind:
On the new installation (the working one), I opened the 839 port (related to the mail server) in the DMZ on the firewall.
I thought it was the difference, but I was wrong.
I repeated the installation on the VM Ubuntu, and it still doesn't work.
Now I'm pretty sure there are no differences between the two ubuntu server configuration.
I would prefere to use a VM installation, but I cant get crazy about it... |