Remittances state 'done'/sent, but some are not received by suppliers

When carrying out accounts payable payments, we send remittances to each supplier individually when we process their payment.

There have been multiple occasions where suppliers have reached out about not receiving a remittance, but MYOB lists it as 'done' and there are no errors received back via our emails stating that it was not being able to be sent.

This has been ongoing and is intermittent.
I would love to know if there is a solution.

Thanks