'Returns C{True} if the message has a BCC address matching the query.
@type query: A L{list} of L{str}
@param query: A list whose first element is a BCC L{str}
@type id: L{int}
@param id: The sequence number of the message being checked.
@type msg: Provider of L{imap4.IMessage}'

def search_BCC(self, query, id, msg):

    bcc = msg.getHeaders(False, 'bcc').get('bcc', '')
    return (bcc.lower().find(query.pop(0).lower()) != (-1))
