There seems to be something wrong on the Outlook servers. Hopefully they fix this quickly on the server. I've see a few reports similar to yours and I can confirm it myself. This looks like a problem with OCSP stapling on the server because it works when I disable this feature in Firefox. *https://en.wikipedia.org/wiki/OCSP_Stapling *https://blog.mozilla.org/security/2013/07/29/ocsp-stapling-in-firefox/ You can temporarily toggle this pref to false on the <b>about:config</b> page to see if disabling OCSP Stapling works for you. It is best to reset this pref via the right-click context menu to true once you are done with the this website. *security.ssl.enable_ocsp_stapling = false You can open the <b>about:config</b> page via the location/address bar. You can accept the warning and click "I'll be careful" to continue. *http://kb.mozillazine.org/about:config

Thanks for your help. I contacted Microsoft ( what a waste of time ) & of course they said it is a Firefox problem.