postfix sends mail to local server but nowhere else

I got post fix to send mail to the local email server, but when I try and send it out to one of my other domain name email addresses, I check the mail log and it's there, but I check my box and it's not. I am using Mail to send email from my local server, but when I try and send mail via PHP it's a no go. Any ideas? if you need me to post some files, let me know.

Thanks for the help.

Also, my ISP has blocked port 25
and I've already tried doing this and couldn't get it to work.

http://www.gungeralv.org/notes/arch..._relay_host.php