Setting up email is a pain

So I was trying to create a "Contact Us" page in my LS Enterprises site. I found a couple of tutorials online that were pretty straightforward, worked through them, and eventually cobbled together a basic finished product. It has 3 fields: the sender's email address, the Subject line of the email, and the email body. Below that is the "Send" button, and that's it - no styling so far. In Django, you can configure it to send the email out to the console, so you can run tests and read the emails that are generated in the console. This part works, but when I try to flip it to actually send an email, the system throws an error in a strange way - it only allows emails to be sent that are addressed to the recipient email address, the email address that is hard-coded into the Django backend. So it essentially sends the email from email@domain.com to email@domain.com. Which is useless. Furthermore, it throws an error when you type in any other email address for the sender, i.e. user@otherdomain.com. So the email never gets out of Postfix on the server, and never arrives at the recipient. I've been around and around on this issue for the last 3 days and I can't figure out how to fix it. I've tried reconfiguring Postfix to no avail, it seems as though nothing I change has any effect. So I'm a little frustrated with this now, and I'm thinking of other alternatives. I could use a service like SendGrid to handle the sending of the emails, but I'd have to rely on their free tier of service, which could go away at any time. I'd rather not do that, as I have my own mail server, and it's working properly. I think I'm going to have to re-write a lot of Django code to rearrange things, or else I'm stuck. I'm thinking of things I want to incorporate in the future into my websites. lennyshort.com is a very basic Django-driven site and isn't very impressive, so I'd like to redesign it and use an API to connect the Django backend to a React frontend. I recently worked my way through a book that covered that, so I think I could do it. I also still want to incorporate Markdown into this blog to make it prettier, plus setup an Ansible server to administer the Cisco switches and routers I have in my cabinet at work. But it seems that no matter what I try, I eventually run into an issue like this email problem that I can't solve. I posted a question on ServerFault about this and got one reply, which I appreciate, but I'm still stuck on this one. Anyone got any ideas?