SMTP fails on localhost

Guys, I appreciate the answers, but it appears none of you really examined the issue (the things I've posted).

No, the problem is not about an antivirus software. As I said, the email class in CI3 works, but the one in CI4 didn't work. This suggests that the problem is/was about CI4.

The code I've posted above is not arbitrary. It's something that I've tested. And I'm using the port 587. Also, I've mentioned using XAMPP. So all this is on dev/localhost.

Of course, it works on a live server (probably because you have a certificate there).

There's nothing wrong with the email server. The code works on a live server.

The problem is about the way email class in CI4 works. It's not the same as the email class in CI3.

I've already found the source of the problem, and managed to work around it. Now, all I need is an explanation.