Imports System.Text.Regularexpressions
 
' ...
 
Public Function IsValidEmail(email As String) As Boolean
    Return Regex.IsMatch(email, ("^([\w-\.]+)@((" & _
      "\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))(" & _
      "[a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$")
End Function

Ralf