We are using Zimbra as mailbox and all is working ok, but now we need to configure 1 (or two) additional Zimbra server as mta, we need that this server receives all external mail to mailbox server.
I have made some test and i detected that if I configure as mta role with zimbra, then I have a problem if mailbox/ldap is stopped, then mta can't receives any mail and we lost all HA environment -we can't install additional ldap at this momment-. I have detected that mta try to connect to ldap, it seems that try to check is destination address exist.
For security and with previous described problem we think that best solution is to install Zimbra mta as standalone server, and then configure to forward (relay) mail of this domain to mailbox -I have checked and this works-, but with this when is sended a mail to an account that for example not exists return mail is sended for mailbox, and with mta ldap integration seems that mail is sended for mta, and use less resource because is using mta to answer and this mails.
How can I do this with zimbra standalone with mta, is configurable zimbra postfix to read a file or similar that can contains a synchronized a valid user of zimbra?
Ho can I recover users of zimbra to create this script? How can I configure this in postfix?