starting mta failed

[fieze]

I just finished my first zimbra installation and the mta cannot start.
Please I need clues on the problem. Output of zmcontrol start is given below.
[zimbra@mypc ~]$ zmcontrol start
Host mypc.macsonia.local.
Starting ldap...Done.
Starting logger...Done.
Starting mailbox...Done.
Starting imapproxy...Done.
Starting antispam...Done.
Starting antivirus...Done.
Starting snmp...Done.
Starting spell...Done.
Starting mta...FAILED
postmap: warning: valid_hostname: misplaced delimiter: mypc.macsonia.local.
postmap: fatal: file /opt/zimbra/postfix-2.4.3.4z/conf/main.cf: parameter myhostname: bad parameter value: mypc.macsonia.local.
postalias: warning: valid_hostname: misplaced delimiter: mypc.macsonia.local.
postalias: fatal: file /opt/zimbra/postfix-2.4.3.4z/conf/main.cf: parameter myhostname: bad parameter value: mypc.macsonia.local.
postfix failed to start


Starting stats...Done.

[phoenix]

Did you ever set-up a Split DNS as you were told in another thread? Have you got valid DNS A & MX records for your server? Is your hosts file correct? What errors are in the log files?