Hello,
I would like to thank the team at MYOB for finding the solution to my issue. The product specialist called me, we tried to send a couple of trial invoices through the in-built e-mail that still didn't work. He promised to have a look at the data log with his colleagues and to come back to me the next day.
By 17:00 the same afternoon i received the trial e-mails sent earlier in the day and since then the system works.
The product specialist called me the next day to verify that everything is now fine as it appears to be to his end.
Very happy with the result.
Thank you!