Ziggie, you seem to have these things a bit muddled up. Please don't take this as a flame!
Are you sure your ISP blocks you from accessing any SMTP server you want? They might block incoming SMTP (port 25) *to* your computer. Find out exactly what their policy is for port 25 incoming and outgoing.
Fetchmail does not 'grab mail being sent to your domain name.' Your domain name needs to point at an IP address. That IP address needs an SMTP server (like postfix) to accept the mail. If you already have such a server, fetchmail could retrieve your mail from that server. If you don't already have such a server, fetchmail does not do what you are talking about.
Try to state very clearly what it is you want to do, and what you already have set up. I can't tell from reading this if you have an email server, somewhere, for your domain, or not.
"postfix is for picking up mail that I send to my server and relay it out to the internet though my isp" - Please explain what 'my server' refers to. Postfix is for receiving mail and sending mail. It doesn't need to relay mail through your ISP. It doesn't 'pick up' mail if by that you are thinking of POP or IMAP.
If you want to handle mail for yourdomain.com, here's what you do:
Point yourdomain.com at your IP.
Open port 25.
Tell Postfix to accept mail for yourdomain.com.
Use procmail to sort delivery.
Use postfix to send mail.
If you just want to retrieve mail from an account you have on someone else's server, and send mail directly from your box, you:
Use fetchmail to retrieve your email.
Install postfix and use it to send email directly from your box. Keep port 25 closed.
"The main thing that I want to do is to grab mail that are being send to may domian name". Explain this. Is there already a server accepting mail for that domain, or not?
This might be all greek to you. Just try to be more clear about WHAT you want to do. Be careful saying 'the server' , 'my server,' etc., because right now it is very hard to understand you.
