Client receiving another clients MYOB linked purchases in their intray

Hello 

One client of mine has regular invoices from a supplier who is also on MYOB.

We created the myob to myob link which has been working fine

A few months ago another client said I had accidenatally been adding the purchases to their intray instead. I now realise the the error is with MYOB

How can I stiop the wrong client from receiving these supplier purchases in their in tray? BTW the correct client is also receiving them which makes me worry how many other clients may be incorrectly receiving them too!