It may be that, if you're at work, someone set up MIME::Lite to use the optional module that comes with MIME::Lite called MailTool.pm. It's a subclass of MIME::Lite which doesn't provide any new methods, instead it supposedly "enhances" MIME::Lite's existing ones. Basically, it changes the default send method from sendmail to smtp. Check out the docs that davorg mentioned to see how to do send_by_smtp.

Update: I'm sorry. I didn't catch the Windows backslashes. It's been a long day...