How can I prevent emails sent via wordpress wp_mail from being sent to spam?

How can I prevent emails sent via wordpress wp_mail from being sent to spam ?? The company uses wordpress to send emails to people in the intranet via wp_mail. The problem is that all emails received by outlook are in spam, how can I send emails to prevent emails sent via wordpress wp_mail from being sent to spam ??
The company uses word press to send emails to people in the Intranet using wp_mail. The problem is that all emails received in outlook are in spam,
Ask how to send emails to inbox!

(By the way, how does the client identify spam ??)

------ Solution --------------------
What is spam?

IT. SOHU. COM