A simple way is to click edit>find>search messages, and then search for that email address and when search is done, highlight and delete. Do for inbox and repeat for sent folder.

I do not know what you mean by edit/find/search. I am not aware of any 'edit' button.

You can also do this with tools>search messages . the edit feature is on the menu bar..

Menu bar?

At the left I have a bar with General Address book Calendar Tasks

and at the bottom Settings Hide space toolbar

Then there is something that shows 'Folder modes'.

I do not know of a menu bar or edit button

As I mentioned, the feature is at tools>search messages. the menu bar is hidden by defaul by can be viewed by pressing alt key. you can make it the default by then clicking view>toolbars and ticking menu bar.

I am struggling with it and it does not seem to work easily, but if it does work at all no doubt I shall get used to it. Thank-you.

Are you having trouble with the search feature? Let me know and I'll try to assist in walking through the steps

No matter. Now I have found it I shall sort myself out in time, thanks anyway.