Hi to all. I can't send email outside the network but I can send in localhost. Could this be an DNS issue? I can browse website but can't send email. Below is the logs:

Mar 26 15:44:16 abruzzi postfix/pickup[4346]: CFE7BFEFA: uid=1000 from=<nelson>
Mar 26 15:44:16 abruzzi postfix/cleanup[5189]: CFE7BFEFA: message-id=<20070326074416.CFE7BFEFA@abruzzi>
Mar 26 15:44:16 abruzzi postfix/qmgr[4347]: CFE7BFEFA: from=<nelson@mail.abruzzi>, size=344, nrcpt=1 (queue active)
Mar 26 15:44:46 abruzzi postfix/smtp[5191]: connect to f.mx.mail.yahoo.com[209.191.88.247]: Connection timed out (port 25)
Mar 26 15:45:16 abruzzi postfix/smtp[5191]: connect to c.mx.mail.yahoo.com[68.142.237.182]: Connection timed out (port 25)
Mar 26 15:45:46 abruzzi postfix/smtp[5191]: connect to a.mx.mail.yahoo.com[209.191.118.103]: Connection timed out (port 25)
Mar 26 15:46:16 abruzzi postfix/smtp[5191]: connect to b.mx.mail.yahoo.com[66.196.97.250]: Connection timed out (port 25)
Mar 26 15:46:46 abruzzi postfix/smtp[5191]: connect to g.mx.mail.yahoo.com[206.190.53.191]: Connection timed out (port 25)
Mar 26 15:46:46 abruzzi postfix/smtp[5191]: CFE7BFEFA: to=<ntsera@yahoo.com>, relay=none, delay=150, delays=0.07/0.01/150/0, dsn=4.4.1, status=deferred (connect to g.mx.mail.yahoo.com[206.190.53.191]: Connection timed out)

Take note that mail.abruzzi is not a qualified domain.

looks more like a firewall issue. can you telnet to the servers on port 25 manually? "telnet 209.191.118.103 25" you should get some form of SMTP banner if you can. dns doesn't look at fault, as unless the A records are WRONG they've been resolved to IP addresses just fine.

doesn't look like it (DNS) judging by this:
f.mx.mail.yahoo.com[209.191.88.247]
seems to have resolved the name.