Help sendmail

[vdingo11]

After a system upgrade (to Fedora 16) sendmail not working properly.
When I try to send an email with php mail function (php file is on local machine) in / var / log / maillog write:

Feb 8 20:39:56 nume_domeniu sendmail[20796]: q18Iduuh020796: from=apache, size=127, class=0, nrcpts=1, msgid=<201202081839.q18Iduuh020796@nume_domeniu.ro >, relay=apache@localhost
Feb 8 20:39:56 nume_domeniu sendmail[20797]: q18IduBF020797: from=<apache@nume_domeniu.ro>, size=400, class=0, nrcpts=1, msgid=<201202081839.q18Iduuh020796@nume_domeniu.ro >, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1]
Feb 8 20:39:56 nume_domeniu sendmail[20796]: q18Iduuh020796: to=nume_cont@yahoo.com, ctladdr=apache (48/48), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30127, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (q18IduBF020797 Message accepted for delivery)
Feb 8 20:39:57 nume_domeniu sendmail[20799]: q18IduBF020797: to=<nume_cont@yahoo.com>, ctladdr=<apache@nume_domeniu.ro> (48/48), delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=120400, relay=mta5.am0.yahoodns.net. [74.6.136.65], dsn=5.0.0, stat=Service unavailable
Feb 8 20:39:57 nume_domeniu sendmail[20799]: q18IduBF020797: q18IdvBF020799: DSN: Service unavailable
Feb 8 20:39:57 nume_domeniu sendmail[20799]: q18IdvBF020799: to=root, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31653, dsn=2.0.0, stat=Sent

What could I do?

[DrHappyAngry]

It looks like it's refusing the connection on their end or it's blocked. You can see it gets up to the point where it tries to talk to yahoo's server but gets denied or blocked for some reason.

See if the port's opened from where you're at. Just telnet to a remote mail server on port 25 and see if you get a response. A lot of ISPs block port 25 outbound to anything but their mail servers. It could also be yahoo refusing you since nume_domeniu.ro doesn't map to anything in dns. They probably also won't accept mail from you unless you've got a reverse DNS entry for your IP address that matches what your mail server says it is.

It could also be your own iptables or other firewall rules, so you might want to check those.