Mail downloading all messages when deleting

My mail program seems to be doing weird stuff that I am pretty sure it never used to do.

I leave messages on my server (pop account) necause I use more than one computer.

Occasionally however I know that I have everything I need so delete all messages from the server in order to prevent downloiading them again when I go to another computer.

This is where the weirdness starts. When it removes the messages from the server, it downloads them all, often a few thousand, even if it has downloaded them already, like when it was originally received. I have been using this procedure for a number of years and it never used to do this.

Basically now whenever I remove old messages from the server I get my system collged up with thousands of "unread" messages that in fact have been read, it just decided to download them all again.

Any idea why it is doing this and how I bloody well stop it?

By the way I see there is no discussion group for mail in this new version of discussions, so I figured here is as good a place as any.

Thanks in Advance,

Sean