I've been using Thunderbird without issue for business for nearly eight years now. I currently run it on a lap top with Windows 7 Pro. There is only one account/e-mail address on Thunderbird. This morning when I went to check my e-mail I was prompted for my password then received the error "Sending of password did not succeed. Mail server exchange.company.com responded: Logon failure: unknown user name or bad password." I retried the password, restarted Thunderbird and tried it again but still received the same error. I sent a test e-mail from Thunderbird which went through just fine. I'm also able to log on to the exchange server via web browser and I am able to send and receive e-mail on my mobile device. I've cleared all of the saved passwords from Thunderbird and I've verified the account settings but I'm still unable to download any e-mail to Thunderbird. Apart from deleting the account, I'm not really sure what to do here. Any help would be much appreciated!! Thanks.