I am using some services online, where i didnt get email confirmation mails from. they simply would never arrive at zoho. I then used my gmail email address instead. I always accepted this weird issue with zoho mail.

Now, i made a new domain, and im also trying to send emails towards my zoho domains as a test, and i notice that i get instant mail delivery failures back, that the email cannot be send.

I tried gmail and outlook, and those get my emails fine. I might add that its neither flagged as spam, they arrive 100% fine.

So there is definitely something wrong somewhere, and i'd love to find out what it is.