1 . 3 1 ▁was ▁added ▁with ▁Microsoft ▁Mail ▁for ▁PC ▁Network s ▁version ▁ 3 . 2 , ▁and ▁a ▁mult it ask ing ▁M TA ▁for ▁Windows ▁N T ▁was ▁added ▁with ▁version ▁ 3 . 5 . ▁This ▁ran ▁in ▁the ▁OS / 2 ▁sub system ▁of ▁Windows ▁N T ▁and ▁Windows ▁ 2 0 0 0 , ▁and ▁consisted ▁mostly ▁of ▁the ▁Version ▁ 3 . 2 a ▁External ▁with ▁wra ppers ▁containing ▁hook s ▁allowing ▁control ▁by ▁N T ▁administration ▁util ities . ▁ ▁The ▁database ▁design ▁and ▁pass ive ▁nature ▁of ▁the ▁server ▁both ▁created ▁several ▁weak ness . ▁A ▁complete ▁lack ▁of ▁distinction ▁between ▁" header " ▁and ▁" en velope " ▁address ing ▁data ▁meant ▁that ▁now - standard ▁functionality ▁such ▁as ▁B cc : ▁could ▁not ▁be ▁implemented . ▁Mail ing ▁lists ▁were ▁similarly ▁problem atic . ▁Also , ▁a ▁single ▁post office ▁was ▁limited ▁to ▁ 5 0 0 ▁mail box es ; ▁a ▁large ▁enter prise ▁would ▁require ▁many ▁post off ices ▁and ▁many ▁M T As ▁to ▁connect ▁these ▁post off ices . ▁Since ▁sched uling ▁data ▁and ▁address ▁lists ▁were ▁also ▁stored ▁locally ▁in ▁these ▁post off ices , ▁moving ▁schedule ▁and ▁global ▁address ▁book ▁information ▁required ▁yet ▁more , ▁separate ▁agents ▁called ▁Dis patch ▁and ▁Microsoft ▁Sch edule + ▁Distribution ▁Agent . ▁Dis patch ▁would ▁synchron ise ▁the ▁various ▁copies ▁of ▁the ▁Global ▁Address ▁List ▁using ▁MS Mail ▁ 3 . x ▁Directory ▁S ynchron ization ▁Pro tocol .