connection timed out

Good day.

our problem started last week. postfix suddently could not send
Internet email but can recieve them.

when we checked maillog, we get the following:
May 16 19:11:24 svr1 postfix/smtp[1876]: connect to
mailin-01.mx.aol.com[205.188.155.89]: Connection timed out (port 25)
May 16 19:11:24 svr1 postfix/smtp[1876]: 78B50A0366:
to=3D<balatinsayo@aol.com>, relay=3Dnone, delay=3D271429, status=3Ddeferred
(connect to mailin-01.mx.aol.com[205.188.155.89]: Connection timed
out)

we have checked the firewall and iptables -- port 25 is allowed.=20
checked main.cf -- it was not modified. checked rbls.org -- our ip is
not blacklisted. i was able to test telnet to a mail server at port
25 -- i was able to send email thru telnet. postfix is listening at
port 25.

any clue is appreciated as we don't know what else to look at.

thanks.