I Just Received An Email That Was Marked As Spam, But It Isn't. Why Did This Happen?

I just received an Email that was marked as spam, but it isn't. Why did this happen?

No filtering system is perfect. In this case the message sent met the qualifications of looking like spam to our rules-based system. In the future we will be offering user-by-user Email whitelist to allow messages to go through without being marked.