not receiving mails from a domain

Hi,

why some of the mails sent to me are not shown to me from my domain?

When I sent a reply (from domain) to a mail (from outlook) it came in outlook.

When I added my domain mail to safe senders list, then the mails from this email id is coming to outlook.

But when removed from safe senders list, the mails are not shown.

I am even not getting a delivery rejection notice in my domain email.

Any clues why mails from this domain are hidden?

Regards
Aby