Get-ExchangeServer | fl name,AdminDisplayVersionThe output will look something like this:
The AdminDisplayVersion value tells you the Exchange version using the following ww.xx.yyyy.zzz format:
MajorVersion | ServicePack | CumulativeUpdate/UpdateRollup | MinorVersion
For example, 14.3.0123.004 is Exchange 2010 Service Pack 3, 15.0.1178.004 is Exchange Server 2013 CU13, and 15.1.0466.034 is Exchange Server 2016 CU2. You can refer to Exchange Server Updates: build numbers and release dates to determine the exact version of Exchange is running. You can also run the Get-ExchangeServerBuildNumbers cmdlet in Exchange 2013 or Exchange 2016. This cmdlet scrapes the same webpage and displays the Product Names, Release Dates, and Build Numbers for every version of Exchange Server going as far back as Exchange Server 4.0 Standard Edition, released on June 11, 1996. Worth memorizing if you want to win one of Tony Redmond's famous Exchange trivia contests. :)
Note that Exchange 2013 CU4 was released as "Exchange 2013 Service Pack 1", but the ServicePack build number did not really increment until Exchange 2016 to 15.1, further demonstrating that Exchange 2016 is really just an incremental upgrade to Exchange 2013.
But what if you don't have easy access to EMS, or you want to check the version of the Exchange Server your mailbox is hosted on in Exchange Online for some reason?
If your on-prem Exchange 2013/2016 organization is using MAPI over HTTP (and you really should be) you can use the following URL to check which version of Exchange is running on the server hosting your mailbox:
https://<serverFQDN>/mapi/emsmdb/For Office 365 use https://outlook.office.com/mapi/emsmdb/
The output will show the server version number, as shown below.
The cool thing about this method is that even works externally as long as Outlook Anywhere is published to the Internet. Keep in mind that the version returned is for the server hosting the mailbox being accessed, not the front-end client access proxy server. You can tell which front-end CAS your hitting by observing the Cafe server value.
Note that this method won't work if you haven't configured MAPI/HTTP or for mailboxes hosted on Exchange 2010 or earlier because they don't support MAPI over HTTP.