Hi Support
i have set it up the zimbra server Release 7.2.3_GA_2872.RHEL6_64_20130304144847 CentOS6_64 FOSS edition when I change disable_dns_lookups=yes by "postconf -e disable_dns_lookups=yes" command on my server it was a problem i cant send gmail,hotmail,yahoo and i try to set it back the default setting "postconf -e disable_dns_lookups=no" I get it problem :7025 timed out error and all Incoming Mail cant receive

Incoming mail when setup disable_dns_lookups=no (can send every doamin)
May 7 19:40:29 wemail postfix/lmtp[10526]: 890EFF20FEE: to=<ming@cncl.com.hk>, relay=none, delay=63, delays=0.11/0/63/0,
dsn=4.4.1, status=deferred (connect to mail.domain.com [203.x.x.x]:7025: Connection timed out)

Outgoing to gmail when setup disable_dns_lookups=yes (cant send gmail,hotmail,yahoo but other domain is work fine)
May 8 16:37:24 mail postfix/qmgr[18031]: 4C12CF21304: from=<ming@cncl.com.hk>, size=2955, nrcpt=1 (queue active)
May 8 16:37:26 mail postfix/smtpd[11630]: disconnect from n1164832125.netvigator.com[]
May 8 16:37:54 mail postfix/smtp[11634]: connect to gmail.com[]:25: Connection timed out