Spam is a term usually associated with unsolicited or undesired email messages. How is that related to Firefox? Firefox doesn't do email. Web mail services software has a "Spam" button for disposal of those types of messages, and that software usually adds the "sender" of those messages to a "blocklist".

If you are talking about web forgeries or phishing websites, which try to fool you into thinking they are legitimate, open Help > Report Web Forgery... while you are viewing a web page and report that web page.

I'm talking about an email sent to my computer email service wondering if it is a phish...it's from mozilla@awesomeness,mozilla.org? I clicked on the download new version of Mozilla, but immediately closed before I did anything to make sure it was legit first. Help?