Windows上用于生产服务器的良好SMTP服务器

I'm going to have my website hosted soon on a VPS or dedicated server (with Windows 2008), so I'm trying to plan ahead. I wonder whether the built-in SMTP server that comes with IIS7 is reliable enough for a production server or should I look for an alternative? I heard good things about hmailserver and best of all it's free, do you have any experience with using the bulit-in SMTP on a high traffic website.I'm going to have my website hosted soon on a V