Message unsubscribe function and email address verification

<%
Dim email
Email=request.form ("email")
If IsValidEmail (email) Then
If Request ("action") = "unsubscribe" Then
Response.Redirect "Del_email.asp?email=" &email
Else
Response.Redirect "Add_email.asp?email=" &email
End If
Else
' Response.Write ' Invalid email format, please press "back" button to refill a valid email "
Response.Write "<script Language=javascript>alert (' invalid e-mail format, please refill a valid email! ');"
Response.Write "Javascript:history.go ( -1) </SCRIPT>"
End If

function IsValidEmail (email)
Dim names, Name, I, C
' Check for valid syntax in ' to email address.
IsValidEmail = True
names = Split (email, "@")
If UBound (names) <> 1 Then
IsValidEmail = False
Exit function
End If
For each name in names
If Len (name) <= 0 Then
IsValidEmail = False
Exit function
End If
For i = 1 to Len (name)
c = Lcase (Mid (name, I, 1))
If InStr ("abcdefghijklmnopqrstuvwxyz_-.", c) <= 0 and not IsNumeric (c) Then
IsValidEmail = False
Exit function
End If
Next
If left (name, 1) = "." or Right (name, 1) = "." Then
IsValidEmail = False
Exit function
End If
Next
If INSTR (names (1), ".") <= 0 Then
IsValidEmail = False
Exit function
End If
i = Len (names (1))-InStrRev (names (1), ".")
If I <> 2 and I <> 3 then
IsValidEmail = False
Exit function
End If
If INSTR (email, "...") > 0 Then
IsValidEmail = False
End If
End Function
%>