▁Mail ▁product , ▁Microsoft ▁Mail ▁for ▁PC ▁Network s ▁v 2 . 1 , ▁was ▁introduced ▁in ▁ 1 9 9 1 . ▁It ▁was ▁based ▁on ▁Network ▁Cou rier , ▁a ▁L AN ▁email ▁system ▁produced ▁by ▁Cons um ers ▁Software ▁of ▁V ancouver ▁BC , ▁which ▁Microsoft ▁had ▁purchased . ▁Following ▁the ▁initial ▁ 1 9 9 1 ▁re brand ing ▁release , ▁Microsoft ▁issued ▁its ▁first ▁major ▁update ▁as ▁Version ▁ 3 . 0 ▁in ▁ 1 9 9 2 . ▁This ▁version ▁included ▁Microsoft ' s ▁first ▁Global ▁Address ▁Book ▁technology ▁and ▁first ▁network ed ▁sched uling ▁application , ▁Microsoft ▁Sch edule + . ▁ ▁Vers ions ▁ 3 . 0 ▁through ▁ 3 . 5 ▁included ▁email ▁clients ▁for ▁MS - D OS , ▁OS / 2 ▁ 1 . 3 1 , ▁Mac ▁OS , ▁Windows ▁( both ▁ 1 6 ▁and ▁ 3 2 - bit ), ▁a ▁separate ▁Windows ▁for ▁Work groups ▁Mail ▁client , ▁and ▁a ▁D OS - based ▁Rem ote ▁Client ▁for ▁use ▁over ▁pre - PP P / pre - S LI P ▁d ial up ▁mode m ▁connections . ▁A ▁stri pped - down ▁version ▁of ▁the ▁PC - based ▁server , ▁Microsoft ▁Mail ▁for ▁PC ▁Network s , ▁was ▁included ▁in ▁Windows ▁ 9 5 ▁and ▁Windows ▁N T ▁ 4 . 0 . ▁The ▁last ▁version ▁based ▁on ▁this ▁architecture ▁was ▁ 3 . 5 ; ▁afterwards , ▁it ▁was ▁replaced ▁by ▁Microsoft ▁Exchange ▁Server , ▁which ▁started