i have this problem since few months apparently and i realized it after few product sales that i wasn't notified about in mail although it worked before. 
domain : Royalsafari.net

i have wordpress + woocommerce 
sending mails once successful product purchase or any reservation. 
i installed WP MAIL LOG plugin and it shows all mails are sent successfully from WP 
i tested it out on Gmail & Hotmail it delivers but not to mails @RoyalSafari.net 
i tested sending normal mails to ........ @RoyalSafari.net it delivers also 

i checked the blacklist, added to white list, added to trusted domain 
nothing made any difference !! it's just zoho not receiving any mails sent from my domain to mails registered with same domain name.