The email system was working perfect;y for my 2 Comcast.net email accounts. I needed to change one of the passwords. Now for this account, all I get is the message "Login to Server Imap.Comcast.Net with username [my email address] Failed". Sometimes, when I enter the password, Thunderbird accepts it and loads any new emails...but within a few seconds, I get the failure message again. I have rebooted my Dell desktop several times with no luck. I have also discussed this with Comcast support who tell me that the Thunderbird system needs to be optimized...whatever that is. Any assistance would be appreciated.