I have config one ldap , one mta and one mailbox server. orginally i thought i dont habe mailboz sever ..so i install ldap>mailbox> then mta , but same error.

the mta server always prompt out

You are configuring this host as an MTA server, but the specified mailstore
used for authentication has not been configured to run the mailbox service yet.
This will cause smtp authentication to fail.

To correct this - after installing a mailstore server,
reset the zimbraMtaAuthHost attribute for this server:
/opt/zimbra/bin/zmprov -r -m -l ms 2.zimbra.com zimbraMtaAuthHost 3.zimbra.com

Once done, start the MTA:
zmmtactl start

ERROR: service.INVALID_REQUEST (invalid request: specified zimbraMtaAuthHost does not correspond to a valid service hostname: 3.zimbra.com)