Could you test two different scenarios to see whether the problem recurs and let us know what happens:

(1) Private browsing window

A private window should not used any cached credentials for the server. You can open a new private window using the menu or by pressing Ctrl+Shift+p

(2) A new secondary Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder.

This will be set up in parallel to your current profile folder.

Exit Firefox and start up in the Profile Manager using the Windows Run dialog (hold down the Windows key and tap R), type or paste the following and press Enter:

firefox.exe -P

When the Profile Manager displays, don't delete anything!

Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, assign a name like TEST082215, and skip the option to relocate the profile folder. After creating the profile, select it and start Firefox in that profile.

Any improvement in accessing OWA?

When returning to the Profile Manager, you might be tempted to use the Delete Profile button. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

Hi jscher2000 Thank you so much for your prompt response. I tried both options. Unfortunately the same problem persists. I appreciate your assistance.

Perhaps there is a proxy such as ISA in front of OWA, or maybe you need to use a VPN?? Can you get support from your IT on this or do they not support using Firefox?

I'm not sure what version of Exchange this is on, but if it still says Outlook Web Access instead of the newer Outlook Web App, you might need to use IE. Firefox only had a limited UI in Outlook Web Access.

But Firefox stopped accessing OWA a week ago after an update. I have no problem accessing OWA using IE or Edge or Chrome. But I prefer Firefox because it's faster than others.

Firefox 40 did change something that affects authentication: it no longer pops up a username/password dialog to prompt for credentials for embedded resources if they are hosted on a different server. These can include a framed page, an external script, or an image, for example.

If you right-click the error page, does "This Frame" appear on the menu? If so, could you follow that and Open Frame in New Tab to see whether it is hosted on a different server? If you reload the page without the frame, does it work normally?

If you cannot work around the problem by unframing the page, you can undo the change as follows. Of course, please be suspicious of this prompt appearing on other sites where it may be to trick you into revealing your credentials to a different site.

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste auth and pause while the list is filtered

(3) Double-click the network.auth.allow-subresource-auth preference and edit the 1 to a 2 and click OK

• 1 shows the login dialog only for framed pages, images, etc., hosted on the same site
• 2 allows the login dialog for framed pages, images, etc., hosted on any site

Does that change anything with your OWA server? If not, you can restore that setting to its default value; it must be something else.

Hi jscher2000 Problem solved. Many thanks for your assistance.