One of the things we’ve learnt the hard way is that if you send emails to some people and organisations, not only will they not acknowledge them, but, if the need arises, they will swear on a stack of Bibles that they never got them.
They can have 10 email addresses, and 100 emails can be sent using each of them and they will say they never got one of them.
If you’ve sent an email to a person or an organisation and, after 14 days, you haven’t got even an acknowledgement, you have to assume that they are one of these.