What's the problem?
One or more of your mail servers isn't implementing SMTP correctly.
Looks like victor.hou [126.96.36.199] works fine; cfood.hou [188.8.131.52] has the problem. Other hosts which have gotten through in the last month are: blubl, alfa, royce, snday.
The problem is not that cfood.hou implements SMTP incorrectly, but rather than due to the high volume of mail that cfood.hou sends out, it gives up on your server during the GreetPause.
maillog.7.bz2:Dec 26 23:48:19 cfood postfix/smtp: 4BD5625A67FA: to=<jmhayes@REMOVED>, relay=REMOVED[REMOVED]:25, delay=307194, delays=307189/0.01/5.1/0, dsn=4.4.2, status=deferred (conversation with REMOVED[REMOVED] timed out while receiving the initial server greeting)
It will only wait a max of 6 seconds for the SMTP banner and then 5 seconds for a response to HELO.