This is actually a solution, rather than a question; I wanted to share it so that others can find it here. Thunderbird works great with Outlook accounts *IF* IMAP/SMTP are available. But, individual companies that sign on with Outlook can shut off these features, and TB users then have limited options. The Owl add-on can be used to get mail via the OWA mechanism and can sync calendars or address books. But it can't SEND mail if SMTP isn't accessible. The Provider for Exchange ActiveSync add-on is free but can only get calendars and can't get or send mail. Argh. Today, I found DavMail (http://davmail.sourceforge.net): software which interfaces with the Outlook or Exchange server and "fakes" a POP or IMAP and SMTP interface that Thunderbird can use with no add-ons needed. Hallelujah. This works beautifully with my company's Outlook mail and allows me to choose between a server-based IMAP interface and a simple local-download POP interface. Fantastic.