I have 3 accounts on hotmail.com & 2 accounts on outlook.com. Had been downloading emails from all of them through POP in Thunderbird for ages. No problem at all. For last 4 days I am getting the following error on accessing mails from one of my accounts in Thunderbird Sending of password for user firstname.lastname@example.org did not succeed. Mail server pop-mail.outlook.com responded: Authentication failure: unknown user name or bad password. [Error= "AuthFailed:LogonDenied-FederatedStsUnreachable-<X-forwarded-for:188.8.131.52><ADFS-Business-604ms>failed logon error - STSFailure - '<S:Fault xmlns:S='http://www.w3.org/2003/05/soap-enve...:Value></S:Subcode></S:Code><S:Reason><S:Text xml:lang='en-US'>Invalid Request</S:Text></S:Reason><Setail><psf:error xmlnssf='http://schemas.microsoft.com/Passport/] Now the same error occurred in my other hotmail.com account today. I have double checked the email id, the password, the POP settings. Everything is as per book. I can access the mails through the browser & on my Android phone. Any ideas ?