Sorry,
But this is not a Firefox problem, and so not really something we can help with.

• see http://windows.microsoft.com/en-GB/windows/outlook-help#v1h=tab1

Possibly you had a Hotmail account that was re-branded as Outlook. Firefox does not handle email directly itself. If you wish to use webmail you choose a webmail provider and then use the webmail support site if you have problems.

Outlook commonly refers to

1. Microsoft software, often part of MS Office
   http://en.wikipedia.org/wiki/Microsoft_Outlook
2. An outdated email client to some extent looking similar to the above
   http://en.wikipedia.org/wiki/Outlook_Express
3. The new name for Hotmail
   • Hotmail webmail http://en.wikipedia.org/wiki/Hotmail
   • http://en.wikipedia.org/wiki/Outlook.com

Note that MS has changed from Hotmail to Outlook for its email service, so you may need to clear cookies.

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes