Mono Monday : to rhyme with....

....Pie I gather.  Bit brain dead at moment (it's December, what do you expect!) but I SPIED the postman this morning through the definitely not DRY window.  S usually parks across our driveway and delivers around the Close before coming to us.  One card today....didn't recognise the hand writing, Exeter postmark and on opening....it was not written in!!!  So the mystery is "who sent it"?