▁ ▁Client ▁Architecture ▁ ▁Client ▁handling ▁of ▁messages ▁remained ▁incons istent ▁through ▁the ▁life ▁of ▁the ▁product . ▁C li ents ▁for ▁MS - D OS , ▁d ial up , ▁and ▁Mac ▁OS ▁left ▁messages ▁stored ▁on ▁server ; ▁the ▁Windows ▁and ▁OS / 2 ▁clients ▁downloaded ▁the ▁messages ▁instead , ▁using ▁a ▁local ▁file ▁(. MM F ) ▁as ▁storage . ▁While ▁this ▁storage ▁could ▁be ▁located ▁on ▁a ▁file ▁server , ▁the ▁various ▁file ▁lock ing ▁issues ▁meant ▁a ▁user ▁could ▁only ▁login ▁to ▁their ▁mail ▁from ▁a ▁single ▁PC ▁at ▁a ▁time . ▁ ▁Further , ▁the ▁differ ing ▁storage ▁mechan isms ▁made ▁using ▁MS Mail ▁across ▁multiple ▁client ▁architect ures ▁problem atic ▁at ▁best . ▁While ▁the ▁in box ▁could ▁be ▁synchron ised , ▁other ▁folders ▁could ▁not ▁be , ▁meaning ▁that ▁only ▁in box ▁messages ▁could ▁be ▁accessed ▁across ▁the ▁two ▁client ▁architect ures . ▁Pl ans ▁to ▁create ▁a ▁Mac ▁OS ▁client ▁which ▁could ▁access ▁. MM F ▁storage ▁were ▁abandoned ▁before ▁version ▁ 3 . 0 ▁sh ipped , ▁though ▁working ▁- ▁if ▁bug gy ▁- ▁versions ▁did ▁exist . ▁ ▁The ▁Windows ▁and ▁OS / 2 ▁clients ▁were ▁built ▁around ▁an ▁early ▁version ▁of ▁M API ▁called ▁M API ▁ 0 , ▁and ▁could ▁in ▁theory ▁enable ▁the ▁client ▁to ▁talk ▁to ▁any ▁server ▁by ▁replacing ▁the ▁M API ▁DLL ▁with ▁a ▁fully ▁comp li ant ▁DLL ▁for ▁the ▁appropriate ▁system . ▁Un like ▁the ▁Microsoft ▁Mail ▁ 3 . x ▁server ▁product ,