Good day all!
This is a follow-up on my earlier e-mail. Chase Giles was correct:
it was not what we thought it was. It was a case of mailboxes being
full and the system just keeps on resending error messages. 
My thanks to those who sent replies privately or via the list, like
J.D. Falk, Chase Giles and Phil Howard. My sincere apologies to
Myriad.net for their trouble.
William