Thunderbird, running on a PC/Desktop started/ran fine, first thing this morning. After about 1 hour, a text message arrived from BT advising that, "as someone unauthorised tried to access your email account - we've blocked it", together with instructions to create new password. New password created --- then able to RECEIVE, but not SEND. One hour (almost) spent on phone with BT Tech Support - checking port numbers, deleting/creating passwords, and, and, and - resulting in (a) still unable to SEND, but can RECEIVE via T'Bird, (b) able to both send AND receive by (bypassing T'Bird) use of BT Email Website. T'Bird is configured POP3, and two other email accounts (Non-BT) are running successfully via T'Bird on the same PC. Error messages following send in T'Bird below. Any suggestions gratefully received. Thank you, Ian