Unable to send emails to a domain pointed at zoho mail - Please help

Unable to send emails to a domain pointed at zoho mail - Please help

I have one domain managed by zoho mail opiliorecruitment.co.uk and another domain using office365 opilio.co.uk

It has been working for a long time, but today, I have been unable to send emails from opilio.co.uk users to opiliorecruitment.co.uk users. The mail is sent, but never arrives.

Please can someone help urgently as this is disrupting our bsuiness

Thanks

Ben