No, I'm almost certain you can't remove the local mailbox. Perhaps you mean the local New Mail folder? As far as I know, being a crucial part of the system -whether you use it or not - it can't be removed. However, if you're using other local folders anyway, does the existence of this one extra line annoy you that much?

I have set my IMAP Inbox as default inbox. However, the "old" local Inbox still appears in the folder list. Is there any opportunity to change that? I would like to have only the folder structure of the IMAP account in the folder list plus certain local folders where I move messages manually. I would be grateful for any ideas.