Thanks for your response, however, I have not yet solved the problem. Yes,I have followed all the steps in the google dev and in WP Mail SMTP. The error I get is always the same. If this error is so common, which I have found out from the large number of other WP users that have had the same problem going back years, you would have thought that someone would have developed and easy fix by now.
Someone suggested that I should check with my ISP to see if they have block port25 on the shared server. I am still waiting to here back from them. In the meantime,I and still trying lots of other things in an attempt to solve this problem.
Thanks for your help,
David.