My Zimbra server send email ok but can not receive external email

[mindows]

My server Uses ZCS Open Source Edition. It has work good for a month. Ten days ago it couldn't receive email from Internet and could send email to Internet. In forum I have read ask2me007 's CANNOT RECEIVE MAIL,My server have mail loops back to myself error after installed,Not receiving email happened ten days ago.I have not do any change after installition.

[uxbod]

cat /etc/hosts
cat /etc/resolv.conf
dig yourdomain mx
dig yourdomain any
host `hostname ` <- note backticks and not single quotes (type exactly as specified)