Emails not coming to our inbox

Hi there,

We are not AccountRight customers. However, our suppliers who are, are not able to send invoices to our email account through AccountRight. We have worked with our IT department to ensure AccountRight domain is allowed through by whitelisting, however we are still not able to receive the emails. These emails are not hitting our exchange server either for this email address, however are allowed through for other emails on the same domain. 

The rejection email received by our suppliers is the same and is as follows:

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Subject: Undeliverable: Please see invoice for services January 2023

Sorry, email delivery was unsuccessful.

Subject: Please see invoice for services January 2023

Destination: (will provide via private message)

Sent: January 24th 2023, 8:36:24 am

Message:

Diagnostic-Code: rejected

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Could you please advise?

Thanks.