postfix/smtp connect to gmail.com[64.233.171.83]: Connection timed out (port 25) server dropped connection without sending the initial SMTP greeting

Postfix has been configured fine.
The mail is working in the local Domain - mydomain.com


But when I try to send mails to outer domains,it produces the following "TIMEOUT" errors in /var/log/mail/info




Nov 5 23:02:43 mydomain postfix/pickup[30923]: 419941C678: uid=555 from=
Nov 5 23:02:43 mydomain postfix/cleanup[31536]: 419941C678: message-id=<20071106050243.419941C678@mydomain.com>
Nov 5 23:02:43 mydomain postfix/qmgr[22926]: 419941C678: from=, size=330, nrcpt=1 (queue active)
Nov 5 23:03:13 mydomain postfix/smtp[31538]: connect to yahoo.com[66.94.234.13]: Connection timed out (port 25)
Nov 5 23:03:13 mydomain postfix/smtp[31538]: connect to yahoo.com[216.109.112.135]: server dropped connection without sending the initial SMTP greeting (port 25)
Nov 5 23:03:13 mydomain postfix/smtp[31538]: 419941C678: to=, relay=none, delay=30, status=deferred (connect to yahoo.com[216.109.112.135]: server dropped connection without sending the initial SMTP greeting)
Nov 5 23:03:51 mydomain postfix/qmgr[22926]: 419941C678: from=, size=330, nrcpt=1 (queue active)
Nov 5 23:03:51 mydomain postfix/qmgr[22926]: 7C14E1C672: from=, size=533, nrcpt=1 (queue active)
Nov 5 23:03:51 mydomain postfix/qmgr[22926]: CD7961C73C: from=, size=527, nrcpt=1 (queue active)
Nov 5 23:03:51 mydomain postfix/smtp[31538]: connect to yahoo.com[216.109.112.135]: server dropped connection without sending the initial SMTP greeting (port 25)
Nov 5 23:04:21 mydomain postfix/smtp[31546]: connect to gmail.com[64.233.171.83]: Connection timed out (port 25)
Nov 5 23:04:21 mydomain postfix/smtp[31547]: connect to gmail.com[72.14.253.83]: Connection timed out (port 25)
Nov 5 23:04:21 mydomain postfix/smtp[31538]: connect to yahoo.com[66.94.234.13]: Connection timed out (port 25)


Nov 6 23:25:30 mydomain postfix/qmgr[11674]: B5DCA1C693: from=,
size=507, nrcpt=1 (queue active) Nov 6 23:26:00 mydomain postfix/smtp[13277]: connect to hotmail.com[64.4.33.7]: Connection timed out (port 25)
Nov 6 23:26:00 mydomain postfix/smtp[13278]: connect to gmail.com[64.233.171.83]: Connection timed out (port 25)
Nov 6 23:26:30 mydomain postfix/smtp[13277]: connect to hotmail.com[64.4.32.7]: Connection timed out (port 25) Nov 6 23:26:30 mydomain postfix/smtp[13277]: 07D5B1C678: to=, relay=none, delay=83207, status=deferred (connect to hotmail.com[64.4.32.7]: Connection timed out)
Nov 6 23:26:30 mydomain postfix/smtp[13278]: connect to gmail.com[64.233.161.83]: Connection timed out (port 25)
Nov 6 23:27:00 mydomain postfix/smtp[13278]: connect to gmail.com[72.14.253.83]: Connection timed out (port 25)



I messed up with it a lot .

It got solved by replacing

disable_dns_lookups = yes

with

disable_dns_lookups = no

in /etc/postfix/main.cf


And apart from this the the folowing may cause this issue ( I am not sure ).

1. The Server is under Firewall
2. Your Server IP may be listed in some SPAM list
3. Improperly configured "relayhost=" entry
4. The faulty main.cf

etcetera.........