DNS TXT record
E-mailing is not new, but it keeps being a widely-used communication form. It’s the official way companies use to approach clients, employees, providers, etc.
Cybercriminals know it, so they try all sorts of malicious tricks to get into your communications. Spoofing here and there, they can send e-mails on companies or people’s behalf just to use their reputation and trustability to cheat others.
That’s why the SPF (sender policy framework) protocol emerged for making e-mailing a safer game.
You (administrator) have the way to limit who can send messages from the domain, and the recipient can check such authorization to decide and take proper actions. It sounds already less risky, don’t you think so?