Documents lost in the post?

Does anyone know where I can find caselaw which says that :

if it is accepted that a document was posted (by a client) then it must be assumed that the document was received (by the DWP).  I am sure I remember a commissioners decision saying this years ago but can no longer find it.

Any such authorities have been overtaken by Levy v SoS DWP [2006] EWCA Civ 890.  In short, posted does not mean received.  However, if there is evidence of posting, Sealy v Consignia plc [2002] EWCA Civ 878 may assist - there is a reasonable expectation that something sent by post will be expected to arrive within the normal time frames stated for postage (subject to industrial action etc).  Both judgements need to be considered in the round.  As both a Court of Appeal judgements, they are of higher authority than Cmmrs’ & Upper Tribunal decisions.

Levy:  http://www.bailii.org/ew/cases/EWCA/Civ/2006/890.html (on appeal from CG/2973/2004)
Sealy:  http://www.bailii.org/ew/cases/EWCA/Civ/2002/878.html