Disconnect method will disconnect wodPop3 from the
server, canceling any ongoing downloads.
Before disconnection occurs, wodPop3 will delete all
messages you marked for deletion using MarkDelete
property, so do not expect that disconnection should occur
immediatelly!
If you do not call disconnect method, but assume that
wodPop3 would disconnect by itself), messages will not be
deleted, even if you marked them for deletion.