Server :: Postfix Setup - Make Own Email Addresses

It wasn't too long ago that I discovered Linux/Ubuntu (in terms of actually USING it) and I've been completely blown away by the capabilities it puts in the user's hands! To think that someone can take an old desktop from a trash pile (literally, in my case) and turn it into a web server for ZERO dollars is absolutely crazy.

Anyway, I've been using said desktop as a sort of "dummy" machine to learn Linux. I want to be clear that I've got another computer for personal use and that I understand that setting up server software on any computer poses a security risk. Having said that, I have a few questions regarding mail servers and their setup on Ubuntu. Again - I'm comfortable with what I've done so far in Ubuntu (installing packages, terminal interaction, basic usage)

My question is mainly this: if you have, say, a domain name through DynDNS (let's say example123.com) and it points to an Ubuntu system, does something like Postfix enable you to make your own email addresses such as user1@example123.com and have an email server from wherever the Ubuntu system is?

I've been following the basic Postfix setup here and have had success so far (down to the "Adding your local domains to postfix" section) bu wanted to make sure that what I'm intending to do is what I'm doing (haha... i hope that makes sense). That is: get domain name at DynDNS, host pages on LAMPP server, use Postfix to facilitate incoming/outgoing email for that domain name.