Just to check: 1) When you had changed your password, were you asked to log in to the virginmedia web site to verify the new password? (Some providers include this as an extra security check.) 2) Can you now log in to their web site and use their webmail service? 3) In Thunderbird, did you follow the steps described here to remove the old password and save the new one? : http://smallbusiness.chron.com/reset-password-thunderbird-48064.html 4) If you now check your saved passwords in Thunderbird, is the password for the virginmedia smtp server correct? 5) Are all the settings in Thunderbird for the virginmedia smtp server correct, as described here? : http://help.virginmedia.com/system/selfservice.controller?CMD=VIEW_ARTICLE&ARTICLE_ID=2726&CURRENT_CMD=SEARCH&CONFIGURATION=1001&PARTITION_ID=1&USERTYPE=1&LANGUAGE=en&COUNTY=us&VM_CUSTOMER_TYPE=Cable