: delete_all( address, port = 110, account, password )
: delete_all( address, port = 110, account, password ) {|mail| .... }
    POP å򳫤оΥ᡼򤹤٤ƺޤ
    ֥åͿ줿Ϻ˥֥åˤΥ᡼
    ϤޤʲƱǤ

        # example
        Net::POP3.delete_all( addr, nil, 'YourAccount', 'YourPassword' ) do |m|
          m.pop file
        end

