As per my comment elsewhere, by default, Drupal provides a wrapper around php's mail() function. On non-MSWindows boxes the PHP mail() system works by invoking a program on the local system to send the email. In the case of MSWindows, you simply tell PHP where there is an SMTP server to use (but it does not provide for sSMTP/startTLS/authentication).
So an obvious solution is to install a simple MTA which provides a CLI client. nullmailer is a fairly obvious choice.
Alternatively you can configure Drupal to use an SMTP handler instead of 'mail()'. Drupal now offer such a module based on phpmailer.
But if your connection to the SMTP relay is not VERY reliable, or if you'll never need to perform anything more complex to your emails (e.g. tying to SPF, adding signatures, metering) then a proper queuing MTA would be the way to go.