Validating email addresses is a black hole. And even if you were able to determine that validity of the email, you still won't know if it's a working email, or even that person's email (they may have entered someone else's address).
If you still want to do a basic test of syntax the you can go into VBA (may require enabling on the Developer tab on the ribbon) and set a reference to "Microsoft VBSript Regular Expressions 5.5", create a new module and enter this code (I am not skilled in RegEx so I got it from StackOverflow, you can get other RegExs at FightingForALostCause or a full descussion at Regular-Expressions):
Public Function CheckEmailSyntax(ByVal Email As String) As Boolean
Dim regex As RegExp
Set regex = New RegExp
regex.Pattern = "^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,6})$"
regex.IgnoreCase = True
CheckEmailSyntax = regex.Test(Email)
End Function
Then in your project enter something like =CheckEmailSyntax(A1). It will return TRUE for the good ones and FALSE for the bad ones. Sort both columns by the T/F column and delete the FALSE ones. Hope this helps.