Thanks for your response. The only changes to my system have been the normal updates from MS Windows and Mozilla Firefox and my Internet Security (Kaspersky).

I have gone back to my backup database from last month but again when I click on the 'Send Email Messages' at the end of the Mail Merge the screen just blinks but nothing seems to happen - no error message from MS Outlook this time either!

In order to test the system I have restricted the messages to just myself & my wife so that I can see if I have been successful or not.