Thunderbird has been working perfectly for many months and then two days ago I began receiving the following message in Thunderbird related to my MSN account. There have been no changes to the MSN account settings from the day that it was working perfectly and the next day when the error message started appearing. "Sending of password for user [email protected] did not succeed. Mail server pop3.live.com responded: Authentication failure: unknown user name or bad password. [Error="AuthFailed:LogonDenied-FederatedStsUnreachable-<X-forwarded-for:184.96.251.109><ADFS-Business-127ms>failed logon error - STSFailure - '<S:Fault xmlns:S='http://www.w3.org/2003/05/soap-envelope'><S:Code><S:Value>S:Sender</S:Value><S:Subcode><S:Value>wst:InvalidRequest</S:Value></S:Subcode></S:Code><S:Reason><S:Text xml:lang='en-US'>Invalid Request</S:Text></S:Reason><S:Detail><psf:error xmlns:psf='http://schemas.microsoft.com/Passport/]" I have verified that I'm using the correct email address and password in Thunderbird by opening a web browser and logging directly into www.msn.com with my MSN email address and password that are entered in Thunderbird. I have verified that POP is ENABLED in my Settings within the MSN account. I changed the password for the MSN account and then entered this new password into Thunderbird but still same message. The new password gets me right into www.msn.com. I installed Thunderbird on another computer and added my MSN account as a new account and when it attempts to verify the account during the setup there is a message that I'm using a bad user name or password. I use the exact same creds at www.msn.com and get right in. I have a Gmail account and another domain email account in Thunderbird and both of those accounts continue to send and receive emails. Just the MSN account is acting up. Any suggestions for resolving this issue would be greatly appreciated.