Firefox doesn't do email, it's strictly a web browser.

If you are using Firefox to access your mail, you are using "web-mail". You need to seek support from your service provider or a forum for that service.

If your problem is with Mozilla Thunderbird, see this forum for support. https://support.mozillamessaging.com/.../home
or this one
http://forums.mozillazine.org/viewforum.php?f=39

Actually I seem to be using Firefox or Outlook, not sure. do you have any suggestions on what I should use? Thank you melstan

Spammers can forge any "from" name and address they like on a message. Since most users don't block mail sent by themselves, they hope to slip past your spam filter this way.

Unless you see these items in your Sent Items folder, or they list multiple people from your address book, most likely they are not connected to your email account.

That said, it's a good idea to scan your computer for malware, because many users unknowingly get recruited into spamming rings (a bot program on your computer takes commands from the botnet coordinator and sends out the spam, usually without any visible indication). This article lists tools other Firefox users have found helpful: Troubleshoot Firefox issues caused by malware.

By the way, I haven't tried setting up any filters in Outlook.com, and I don't see that listed specifically on the help topics page: http://windows.microsoft.com/en-us/windows/outlook-help

You might try Microsoft's forums if you can't find a way. Here's a targeted search: https://www.google.com/search?q=outlook.com+filtering+rules+site:answers.microsoft.com

Thanks for the info, I'll need to search on how to detect and remove any malware ETC

Hi melstan, you can use the tools listed in the article I referenced. Please be extremely careful about what you test, as there is a lot of fake antivirus on the web that will make your life completely miserable.