Ok basically I'm trying to set up my Linux (SuSE 10.1) so I can send mail through it. Mainly because my ISP doesn't allow me to send more than a certain number of emails at one time (for a mailing list). And well I also just want to learn Linux so fooling around with this stuff should be a good way to teach myself! Anyways, I have Postfix installed, but I'm kinda clueless after that. Really what I'm wondering if it is even possible to run a mail server off of my DSL line (and I think my ISP blocks port 25 too). So is it even possible or should I just look for another solution?
Thanks

You can use the mail server of your ISP as a smarthost to forward email to from your server. This should work in any case and using a smarthost is supported by any MTA.

To receive email you can use a 'redirection service' that sends email to a different port (for a small fee). For this you need to add a DNS entry for the mail to be sent to the redirection service, so they can send it to the other non-blocked port. With iptables you can redirect this traffic to port 25 on the machine. You should contact your ISP if this is OK, since they can detect this work-around easily.

But this won't enable me to surpass the number of e-mails my ISP allows me to send during a specific period of time will it? (My problem being that when I try to send out a mailing list i'm sending it out to let's say 100 people at a time, and my ISP doesn't allow this many e-mails to be sent out in 1 day)

Try using another websites or hosting to create your mailing lists???