Mail Function not working in Centos 6.4

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PHP

hi all ...
Now am working in Centos 6.4 cloud server, am upload the simple PHP mail function in that, but the mail function is not working. Maillog file showing the following error

Sep 11 10:35:17 OP-141 postfix/pickup[12232]: 3F6206091D: uid=48 from=<apache>
Sep 11 10:35:17 OP-141 postfix/cleanup[12262]: 3F6206091D: message-id=<20140911050517.3F6206091D@cloud.choicefone.com>
Sep 11 10:35:17 OP-141 postfix/qmgr[12233]: 3F6206091D: from=<apache@cloud.choicefone.com>, size=7821, nrcpt=1 (queue active)
Sep 11 10:35:17 OP-141 postfix/smtp[12264]: 3F6206091D: to=<svsdinfo@gmail.com>, relay=none, delay=0.38, delays=0.36/0.02/0/0, dsn=4.4.3,
status=deferred (Host or domain name not found. Name service error for name=smtp.gmail.com type=MX: Host not found, try again)

please help me how to fix this.
Thanks for advance.

additional information copied from non-solution below
Now the mail status is send in maillog
but the mail is not delivered
now the maillog is

Sep 11 13:12:51 OP-141 postfix/pickup[12772]: 86B6F60580: uid=48 from=<apache>
Sep 11 13:12:51 OP-141 postfix/cleanup[12790]: 86B6F60580: message-id=<20140911074251.86B6F60580@cloud.choicefone.com>
Sep 11 13:12:51 OP-141 postfix/qmgr[12502]: 86B6F60580: from=<apache@cloud.choicefone.com>, size=7821, nrcpt=1 (queue active)
Sep 11 13:12:51 OP-141 postfix/smtp[12792]: connect to smtp.gmail.com[2607:f8b0:4001:c05::6d]:587: Network is unreachable
Sep 11 13:12:52 OP-141 postfix/smtp[12792]: 86B6F60580: to=<svsdinfo@gmail.com>, relay=smtp.gmail.com[74.125.193.109]:587, delay=0.75, delays=0.19/0.02/0.51/0.03, dsn=5.7.0, status=bounced (host smtp.gmail.com[74.125.193.109] said: 530 5.7.0 Must issue a STARTTLS command first. hg4sm511989igb.15 - gsmtp (in reply to MAIL FROM command))
Sep 11 13:12:52 OP-141 postfix/cleanup[12790]: 4B33960866: message-id=<20140911074252.4B33960866@cloud.choicefone.com>
Sep 11 13:12:52 OP-141 postfix/qmgr[12502]: 4B33960866: from=<>, size=9824, nrcpt=1 (queue active)
Sep 11 13:12:52 OP-141 postfix/bounce[12794]: 86B6F60580: sender non-delivery notification: 4B33960866
Sep 11 13:12:52 OP-141 postfix/qmgr[12502]: 86B6F60580: removed
Sep 11 13:12:52 OP-141 postfix/local[12795]: 4B33960866: to=<root@cloud.choicefone.com>, orig_to=<apache@cloud.choicefone.com>, relay=local, delay=0.39, delays=0.17/0.02/0/0.21, dsn=2.0.0, status=sent (delivered to mailbox)
Sep 11 13:12:52 OP-141 postfix/qmgr[12502]: 4B33960866: removed

please anyone tell me what is the problem going on.