I've had good luck with Outlook Web App on Exchange Server 2010. Exchange 2003 was more primitive and offered less choice. I haven't seen Exchange 2013 yet.

Do you know which version you're dealing with?

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Bypass Firefox's Cache

Use Ctrl+Shift+r to reload the page fresh from the server.

Alternately, you also can clear Firefox's cache completely using:

orange Firefox button (or Tools menu) > Options > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click and choose View Page Info > Security > "View Cookies"
• Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"

In the dialog that opens, you can remove the site's cookies individually.

Then try reloading the page. Does that help?

Thank you. Did all of the above. No change. IE allows me to chose between regular Outlook and Outlook Light. Firefox will not, it's defaulted to use Outlook Light. This is where my main issue is, I need to undo Outlook Light.

See how it's greyed out in Outlook choice? I have no way to undo it.

Changing it from Public to Private computer makes no difference. Btw, same happens on my home PC. It's Firefox doing this.

Here's same page in IE. See how Outlook Light is unchecked? I caught this on time. Firefox won't let me to.

Oh, it's Exchange 2007. We never used that one. I see in the small print it says that you need to use IE6 or higher to avoid Light mode. This probably means that 2007 still used ActiveX controls which are proprietary to IE. I'm not aware of any workarounds.

(But maybe you could agitate for an update? 2010 and 2013 are much better in other browsers and have advantages for mobile users.)