As other said. If you want to see if you can. Yes fun go for it.

Don’t use it for anything important. And know that your ISP will very likely have that port blocked already. And if you call them to ask them to unblock it they are unlikely to be willing to.

This is to prevent scammers and spammers.

Also. Know that even if you were able to. Getting other mail servers to not instantly junk your mail is actually quite difficult or impossible. So your emails would always land in spam, be outright blocked, or be in junk.