problem in sending mail

[Max Ma]

I have a problem in send mail to a domain.
I have two server setup to compare the performance.
First one FC 5 and Second one on FC 6 X 64bit ( which have been modified accordingly).

Both system are working fine for last two three weeks now. But we found that the FC6 X64 version can not send to a specified domain for somereason. And FC5 have not problem both on the same network with the same configuration.

I found the zimbra.log have the following difference:

This is from FC 5
Sep 19 11:44:19 mail postfix/smtp[32192]: 243721270B16: relay=mail.welley.com.hk[218.189.180.130], delay=0, st4001c7fa6f$466163d0$0202fea9@MAX> Queued mail for deliv
Sep 19 11:59:31 mail postfix/qmgr[8647]: D529C12704EA: , size=2335, nrcpt=1 (queue active)

This is from FC 6 X 64
Sep 19 11:56:02 winhead-hk postfix/smtp[15562]: 1999738F85CC: m.hk>, relay=127.0.0.1[127.0.0.1], delay=61, status=sent (250 -09, from MTA([127.0.0.1]:10025): 250 Ok: queued as A9E3438F80
Sep 19 12:01:01 winhead-hk postfix/smtp[15602]: connect to mai8.189.180.130]: read timeout (port 25)

Any way to fix this problem?