Hi there,
I have a perfectly working ZCS installation, however I have noticed that several hundred users (we have over 4k in a single server users are spread all over the world) are sending their emails to user@host.domain.com instead of user@domain.com

Just in case you ask: No, I cannot tell the users not to do it.

This behavior presents the following errors:

All these test were done using accounts on the same server.
User01 using zimbra webmail send a message to user02@mail.domain.com, same zimbra server.
user01 gets "mail for mail.domain.com loops back to myself" from zimbra mta.

So I tried to solve it by:
zmprov cd mail.domain.com zimbraDomainType alias zimbraMailCatchAllAddress @mail.domain.com zimbraMailCatchAllForwardingAddress @domain.com

But the error is:
ERROR: service.FAILURE (system failure: unable to create domain: mail.domain.com)
com.zimbra.common.soap.SoapFaultException: system failure: unable to create domain: mail.domain.com
at com.zimbra.common.soap.Soap12Protocol.soapFault(So ap12Protocol.java:88)
at com.zimbra.common.soap.SoapTransport.extractBodyEl ement(SoapTransport.java:245)
at com.zimbra.common.soap.SoapTransport.parseSoapResp onse(SoapTransport.java:221)
at com.zimbra.common.soap.SoapHttpTransport.invoke(So apHttpTransport.java:251)
at com.zimbra.common.soap.SoapTransport.invoke(SoapTr ansport.java:297)
at com.zimbra.common.soap.SoapTransport.invoke(SoapTr ansport.java:261)
at com.zimbra.cs.account.soap.SoapProvisioning.invoke (SoapProvisioning.java:174)
at com.zimbra.cs.account.soap.SoapProvisioning.create Domain(SoapProvisioning.java:350)
at com.zimbra.cs.account.ProvUtil.execute(ProvUtil.ja va:443)
at com.zimbra.cs.account.ProvUtil.main(ProvUtil.java: 1974)
My server is hosted in public IPs, no nat, no internal IPs, etc.
My DNS server (godaddy) has a valid A for mail.domain.com but for MX I only have @domain.com (as usual).
I do not have a DNS server installed on the zimbra server. I use Godaddy managed DNS.

1- Should I create a MX record for host mail.domain.com, so users can send emails to user@mail.domain.com
2- What can I do to tell zimbra that when a user sends emails to @mail.domain.com should be internally forwarded to @domain.com?

Thanks in advance,