It is not immediately apparent, but OE contains at least 2 different toolbars, and usually even more. Each toolbar can be customized differently to suit the various functions that are available. To customize, double-click a blank spot on the toolbar, or right-click and select Customize.
The first toolbar is the one that appears when you click on Outlook Express (the OE Start Page) in the Folder list. By default there are only 4 buttons, but then there aren't many things you can actually do at the Start Page other than write New Mail, Send/Receive messages, open the Address Book, or Find a message.
When you open a mail folder, OE switches to the Mail toolbar. This toolbar is used for all local mail folders, but not Hotmail folders. Each Hotmail account maintains its own toolbar, as does each IMAP account. Don't bother adding any buttons for news functions to a mail toolbar (or vice versa), as they will simply be grayed out and unavailable. The exception is the button for New Mail Message and that for New News Message. These are always active on any toolbar.
The news toolbar is used by all newsgroups on all news accounts. Don't bother with Move to Folder as that does not work for news messages. Use Copy to Folder instead.
My personal favorite toolbar buttons, all of which work on any toolbar, are the Folder List, the Preview Pane, and the Find Message buttons. Use the Folder List to toggle the full, sizeable Folder pane on/off. The Preview Pane is indispensable for quickly turning off that pane. The Find Message button opens the Advanced Find dialogue.