Protects your domain from hacking or attacks. (required to avoid the spam folder)

Guarantees that your emails have been sent from your domain. (required to avoid the spam folder)

Guarantees your email content isn’t changed after you send it. (required to avoid the spam folder)

Helps email providers know what servers accept your emails. (required to avoid the spam folder)

If you're listed, most of your emails will land in the spam folder.