The Thunderbird InBox shows a new item every few seconds or minutes. Duplicates of entries appear. This happens without apparent reason or trigger. A clean installation of Ubuntu 13.10 was done and, using the built in "software center" of Ubuntu, Thunderbird was installed. There was an appreciable backlog of E-Mail that was downloaded (400 items) and then the number of items began to increase when the operator began to delete selected messages. E-Mail items have grown to over 1000 without any new messages being received. Emptying Trash or doing additional deletions does not improve things. Settings have been reviewed without identifying any abnormality. The server setting is POP. No additional plug-ins, applications, etc beyond those intrinsic to Ubuntu 13.10 plain installation.

Assistance will be greatly appreciated.