Exchange 4.0 (1996)

Exchange 5.5 (1997)

Exchange 2000

Exchange 2003

User mailboxes per server

50–500

200–1000

50–3000

Up to 4000

Average mailbox size

25MB

50MB

75MB

100MB

Average message size

4KB

10KB

25KB

100KB

RAM

Up to 256MB

Up to 512MB

1GB

1–4GB