Did you download Firefox from Mozilla.org ? You may have ad / mal-ware. Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up. ------------- Let’s do a full clean re-install; '''[http://www.mozilla.org/en-US/firefox/all/ Download Firefox For All languages And Systems]''' {web link} Save the file. Then; Using your file browser, open the '''Programs Folder''' on your computer. '''Windows:''' C:\Program Files C:\Program Files (x86) '''Mac:''' Open the "Applications" folder. '''Linux:''' Check your user manual. '''Do Not''' remove the profiles folder. Look for, and rename any '''Mozilla''' or '''Firefox''' program folders by adding '''.old''' to them. Do not rename the '''Mozilla Thunderbird''' folder. After rebooting the computer, run a registry scanner. Then run the installer. If all goes well, remove the OLD folders when you are done. --------- If there is a problem, start your '''Computer''' in safe mode and try again. '''[http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting The Computer In Safe Mode;<br>Free Online Encyclopedia]'''

Firefox from Mozilla does not come bundled with extra stuff like toolbars or applications and such. The mail .com thing could be already on your PC or was inserted by something else.