unable to receive email sent by the same custom domain name

Hey Team

I am rather facing a weird situation.

I have 3 custom domain IDs up and running on zoho mail:

I am not able to receive emails sent using the same domain name IDs I created on zoho mail.

For eg: email sent by rachit.saxena@racsann.com to sunny.jain@racsann.com will never show up on sunny.jain@racsann.com ID

My MX records are updated and I am able to send and receive emails from Gmail, yahoo, etc. I am receiving email from rachitsaxena18@gmail.com on all my IDs.

Urgent help please

Thanks