Why has my mail programme slowed down drastically?

Hi, over the last week my mail programme has become increasingly erratic. It has slowed down so much it is getting impossible to use. When I open it and click on a message that's fine, any subsequent actions after the initial opening take anything from 5 to 20 seconds to initiate. While waiting for the action to take place the programme is frozen. It won't even shut down. I've emptied my junk folder and trash and pared down all other folders to a bare minimum. This took forever. Deleting a message takes up to 10 seconds for it to happen Also on three occasions it has simply refused to send a message. No error message appears it just sits there for ever. And these were not all to the same address. All contributions gratefully received.

Wilf

PS sometimes it takes a while for the programme to open even.

W