I have created an email under zoho with my company name as domain name. 

My other colleagues has created one with company name under Outlook.

However, it seem that I have having problem to send email to outlook, it will always failed to deliver, but at the same time, I am able to received email from these emails.

I received this from the < mailer-daemon@mail.zoho.com>:

This is a permanent error. User Unknown :   "

I am confirm that the receivers email address are active and usable. 

This problem has continuous for several months and it is really inconvenient for me and my colleagues.

Hope to receive a reply/ answer soon!

Thank you very much!!!!!!