Undelivered Mail Returned to Sender

Undelivered Mail Returned to Sender

My website uses a function that automatically dispatches an email to me (admin) when a buyer clicks a button in their account page.  This button is made so that they can confirm they've received their item/service, and my site relies heavily on it.  It used to send from their email to me, but after moving to Zoho, it disallowed this relay so I had to simply change the From email. The only email it works with is admin@domain.com, which is the main email for my Zoho Mail account.

Unfortunately, though it works on the frontend now with no error, the mail is undelivered. I can see it in my "Sent" folder, but no matter what I set the To email to, it fails to send. I've tried admin@domain.com and support@domain.com, but it fails to send to both.

Technically it works because I can still see if they've pressed the button by checking admin@domain.com's Sent folder, but this is bothersome and would rather it actually be sent somewhere so I can filter those specific emails to a desired folder. 


I'm using Magento 1.9 with Zoho as SMTP and would really like to keep using it, as I was having issues with account confirmations being sent to hotmail and outlook before switching over.