The lock icon indicates that the account uses a secure connection and would have been there since you configured the account that way. It has nothing to do with the account being locked. If you look at the address bar in your Internet browser you will see the same lock icon when using a secure site. Check under your '''View '''options and make sure '''Threads '''are set to '''ALL'''. If set to Unread then as soon as you read an email is would be hidden. After that I am not sure what would be hiding your old messages.