I work for a small business with a small budget. We are still running SBS 2003 in house.
The nature of our business requires high availability for our email applications. A free way that we've helped accomplish this is to use Google Apps to host our domains MX records. We then use a POP connector to download the emails and deliver them to exchange.
We do this because we only have one server running SBS 2003 and if that server goes down, we don't want email to bounce. We also only have a cable internet connection (much cheaper and faster than a T1) but that isn't always reliable. We also host our blackberry server internally, need activesync access, OWA access, OutlookAnywhere access and also require that all email is archived (regulatory reasons - we use GFI MailArchiver for this).
The POP connector has proved to be flaky at best. I've tried various programs and there's always something that doesn't work the way we want.
I need to look at options for higher availability of Exchange. I've considered looking at hosted exchange, but I can't give up all the freedom we have (blackberry server connections, archiving, full management of exchange etc). Are there any other options I should consider?