hello carlsonrc, your posting in the firefox support forum - firefox doesn't handle your emails directly. in case you're using thunderbird and have a problem with it, please post your question at https://getsatisfaction.com/mozilla_messaging/ or in case you're accessing your mails through webmail and there was a change in the interface, contact your email-provider to help you further...

I receive over 100 emails a day. Many very important. I need to know who they are from. I cannot sort by Sender anymore. I can still sort by sender in Windows Internet Explorer. Should I uninstall Firefox software or will there be a fix to this problem soon?

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

This is a bit of a guessing game. Are you using Yahoo mail? Gmail? Outlook.com/Hotmail? Each one has its own peculiar interface... could you be specific?

I've randomly attached Yahoo's showing where I find the sort control.