Microsoft Exchange Server 2010 Standard Edition

System Requirements: Microsoft Windows Server 2008 X64 Standard And Enterprise Edition With Service Pack 2 Or Microsoft Windows Server 2008 R2 Standard And Enterprise Edition
Ram: Minimum Of 4 GB Or RAM Per Server Plus 5 MB Of RAM Recommended For Each Mailbox
Hard Disk Space: At Least 1.2GB For Installation; Additional 500MB For Each Unified Messaging Language Pack Installed; 200 MB On System Drive