I can't get my emails to work

Hi everyone.
I recently subscribed to a VPS on Hostinger and installed CyberPanel (Latest Build) with AlmaLinux 8. I made my websites work normally using Cloudflare, but I couldn’t get the emails to work.

And a few moments, I managed to send emails to the Gmail, but not for Outlook for example.

Another problem is that even with DKIM enabled, I receive the message: “Your message isn’t DKIM-signed” on Email Tester.

I suspect that my SSL is not working, because even after following several tutorials, I realized that my links are only “secure” using the Cloudflare proxy, including the URL of the panel itself.
I tried following other tutorials on how to fix SSL, but without success.

Here are images of some tests I did:
Print on Imgur

WP-SMTP didn’t work either:
Print on Imgur

DNS is correctly configured on Cloudflare, including using API.

Sorry for the English, I’m from Brazil.