I have Zimbra 6.0 just installed in CentOS, I have a problem because when I try to send an email to any user i got the following error:

The error that the other server returned was: 550 550 5.1.1 <user@domain.co>: Recipient address rejected: User unknown in virtual alias table (state 14).

If I send an email to that same user alias it works fine (ie, user.alias@domain.co)
I only have one domain defined in the server, I can send emails from any users without problems.

I will appreciate any help,