Unless the contrary is proved, the time at which a document is taken to have been served is--
(a) in the case of a document a copy of which is left in a DX box in accordance with this Part, at the end of the second day following the day on which the copy is so left, or
(b) in the case of a document a copy of which is faxed in accordance with this Part, at the end of the first day following the day on which the copy is so faxed.