Correct method of sending Emails using php mail() function to zoho email address

Correct method of sending Emails using php mail() function to zoho email address

Hello Everyone,

My Name is Rehoboth.
I am an Enterprise Software Developer for an organization in Nigeria who makes use of Zoho mail for her business emails. I have been tasked with building a web application that automatically sends emails to our company's zoho email addresses.

I have been able to get the mail function to send to google and yahoo, but somehow it doesnt get delivered in our Zoho email inboxes.

Please where do you think i am making a mistake.