Gmail is strict in handling email, it wants mail sent from an registered domain.
If you setup a server at home, it will send email through your home router connected to your Internet Service Providers IP. That home ip address resolves to for example: dynamic.cable.fr
So no matter what you change on your server at home, the ip / mailhost you are sending from will always resolve to your home IP.
Gmail and other email services does see that there is a mismatch in origin/host - sender to receiver, so mail goes to spam folder.
Even if you could tweak the DNS of your home iSP, Gmail still might reject it, simply because it's a home-ip. They have all those rules in place, to keep us as much as possible spam-free. Without the reverse-dns, dkim etc everybody could run a mail server and a lot of people would not do run it in a safe way.. leaving their mailservers open for hackers etc.
If you want to run a server with mail etc, I would go out and get a cheap vps, register for a few euro a domain. Important here is that the hosting company allows you to set your own DNS and Nameservers.
This way you can run and experiment with a full fledge server hooked on to the web, with all goodies you can think of imagine doing with it :-)
For a VPS you could take a look at the GCP, (Google Cloud Platform) they allow you to try their service out for free. But you have to figure out everything yourself, by documentation or forums. The good thing is, in your free trial you can mess up, reboot, re-install pretty much as often as you want, till you have things working, since they won't bill you. Is the VPS / Server not working anymore? Delete it from your project page, create a new one and of you go again
One downside to GCP they have the standard port for email 25 blocked. Internal and External You can setup a mailserver by using different ports, but keep that also in mind.