Some people reported to have problems sending mails to people at AOL. AOL has a spamfilter on port 25 blocking all requests to send mail over that port. So we've to change a view settings in postfix to let him try to send over port 587. Please open /etc/postfix/master.cf and comment out the following line:
submission inet n - - - - smtpd
Now run <cli> # /etc/init.d/postfix reload </cli> Done!
Test it from another host or a windows box via telnet.
<cli>
# telnet your-server.tld 25
</cli>
Quit with simply typing quit if connected.
<cli>
# telnet your-server.tld 587
</cli>
If you can connect to both ports all went fine.