Wondering what version of Exchange 2007 or 2010 you're running? There are two options to check your build number, within the Exchange Management Console or with a Powershell command.

Exchange Management Console:

1. Select Server Configuration.
2. In the right pane you see the version number and build number.

Or use the Powershell command:

Get-ExchangeServer | fl name,edition,admindisplayversion

It will show up like:

See this link for build numbers and release dates for Exchange Server by Microsoft.