Delivery issues with my outlook.com account

I am experiencing problems receiving email to outlook.com (custom domain) email address from any other outlook.com address.

To domain: pozyx.com (custom domain - outlook.com managed)

To address: {removed for privacy}@pozyx.com

There is some issue with pozyx.com domain. It started after migration of domain to different registrar. MX records are fine however. I receive emails from other (non-outlook.com) addresses without problems. I have only problem to receive email from other outlook.com address. It seems outlook.com refuses to accept pozyx.com as recipient and I cannot find out why (given that other email providers do not have this problem).

I receive these emails after a while:

Thank you.