Simple regular expression I found and have used succesfully to validate emails submitted to my website.

VB Code:
  1. Imports System.Text.RegularExpressions
  2.  
  3.     Function EmailAddressCheck(ByVal emailAddress As String) As Boolean
  4.  
  5.         Dim pattern As String = "^[a-zA-Z][\w\.-]*[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$"
  6.         Dim emailAddressMatch As Match = Regex.Match(emailAddress, pattern)
  7.         If emailAddressMatch.Success Then
  8.             EmailAddressCheck = True
  9.         Else
  10.             EmailAddressCheck = False
  11.         End If
  12.  
  13.     End Function