Thank you for the reply Zhang.
I managed to sort this out; it appears that this can happen as a result of more than just one cause.
For me I had switched off spam and anti virus checking hence yahoo and hotmail did not like that. Yahoo would mark the mail as spam and hotmail would simply delete it and not show it in the first instance. In the pursuit of resolving this I have learned a lot about DNS and email and for that am grateful.
I also came across this post on serverfault.com http://serverfault.com/questions/434703 … -my-emails
might be of interest to others that experience this or a similar problem.
Kid regards