Thank you Linkmaster for your help.
Did that with each of the four mail accounts. And tried to synchronize and got four messages as below for each mail account:
Unable to logon to the server using Secure Password Authentication. Account: '******', Server: 'mail.optusnet.com.au', Protocol: POP3, Server Response: '-ERR Invalid command.', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC18
(PS I put the asterisks in to protect privacy).
I had a good look through all the stuff in the tools menu. Looked at the options and to be really honest I don't understand a lot of the options I am supposed to be choosing from. I looked up Microsoft Help and was still baffled - eg I really don't understand what IMAPI is. Also I'm not sure which Security features to enable.