i registered zoho mail with my own domain. I can login and access the mail app.

I tried to send email from an outlook email account and an icloud email account. Both emails were not received. 

My plan is free. I also tried to send email from this zoho account to my outlook and icloud email. The results are different.

Outlook: email received. which is marked with a red label "unverified", indicating outlook does not know if this email comes from the sender.

ICloud: delivery report attached

I need to use the service normally. I am also willing the pay with low cost. but i am not sure if the problem will remain after i pay.