Good news is that I was able to get it to send email. Its not enough that I configure postfix to be a relay host but to pass an argument to sendmail to put my yahoo email in the from header (discovered that by accident). As for receiving, I haven't gotten that to work.
I do have a system user named omega13a but in ISPConfig I created an email account
omega13a@fedtrek.com . The MX record, are you refering to the DNS config in ISPConfig? I'm asking because I use dyndns.com to point fedtrek.com to my server and that has a place to edit MX records. I think I have both places configured correctly... Here's some screen shots if they help:
http://www.fedtrek.com/staff/omega13.../ispconfig.png
http://www.fedtrek.com/staff/omega13...ots/dyndns.png (I blured out my IP address in that but I don't know what good that will do since people can get it that easily if they know how...)
I don't know if these help but I'll give them to you anyways:
http://www.fedtrek.com/staff/omega13...ts/servers.png
http://www.fedtrek.com/staff/omega13.../mailboxes.png
http://www.fedtrek.com/staff/omega13...ts/fowards.png