That is a Outlook support email issue to address your login issue not a Firefox browser issue.

What OS? What version of Firefox? What does it show on the page about:support? see screenshot Did you try with Firefox in Troubleshoot Mode?

Did you try clearing the browser cache? https://support.mozilla.org/en-US/kb/how-clear-firefox-cache#

You can try to clear all items for a single site. https://support.mozilla.org/en-US/kb/remove-websites-address-bar-suggestions

Last step if needed, you can refresh Firefox. https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings

I'm in it everyday for work and personal use. see screenshot

You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be careful. If you have a password or other data for that domain that you do not want to lose, make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website, data for that website will be saved once again.

• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox