VBScript Email Validation

<%
'The IsValidEmail function checks for a valid email
'IsValidEmail returns True if the email address is a valid email
'IsValidEmail returns false if the email address isn't proper syntax
'The code is well commented and should explain what is happening

Function IsValidEmail(emailAddress)
'Declare variables
Dim ValidEmail, emailParts, iLoopCounter, emailChar, acceptableChars, last2Chars
ValidEmail = True 'set the default result to True
'acceptableChars are the characters that we will allow in our email
acceptableChars="abcdefghijklmnopqrstuvwxyz.-_@"
'use the Split function to create an array with the @ as the separator
'so if your email was test@tester.com the email would be split into an array
'with the first array element holding "test" and the second "tester.com"
emailParts = Split(emailAddress, "@")
'check to make sure that there is only 1 @ and that there are 2 parts
'remember arrays are zero based
'Using the UBound function will return the highest element in the array
'So if it's a valid email the UBound function will return 1, i.e. 0 start
If UBound(emailParts) <> 1 Then
ValidEmail = false
Else
'Check the length of each part of the email address
'first part can be just one character, 2nd part must be atleast 4
If Len(emailParts(0))<1 OR Len(emailParts(1))<4 Then
ValidEmail = false
End If
'check first character on the left part isn't a "." using Left function
If Left(emailParts(0), 1)="." Then
ValidEmail = false
End If
'check that there is a . in the second part of the email address - .com
If InStr(emailParts(1), ".") <= 0 Then
ValidEmail = false
End If
'We know there's a . now make sure there are 2 characters after the . for valid email
last2Chars=Right(emailParts(1),2)
If InStr(last2chars,".") Then
ValidEmail = false
End If
'check that there shouldn't be a _ in the second part of the email address
If InStr(emailParts(1), "_") >0 Then
ValidEmail = false
End If
End If
'loop through each character of email
For iLoopCounter = 1 to Len(emailAddress)
'Use Lcase & Mid functions, Mid function used to return each individual character
'in the email, and then Lcase converts it into lowercase
emailChar = Lcase(Mid(emailAddress, iLoopCounter, 1))
'Check if the emailAddress characters are acceptable
If InStr(acceptableChars, emailChar) = 0 and Not IsNumeric(emailChar) Then
ValidEmail = false
End if
Next
'check if there is 2 . in a row
If InStr(emailAddress, "..") > 0 Then
ValidEmail=false
End If
'check if there is @. in a row
If InStr(emailAddress, "@.") > 0 Then
ValidEmail=false
End If
IsValidEmail=ValidEmail
End function
%>

<% Response.write IsValidEmail("test@testemail") %>

<% Response.write IsValidEmail("test@testemail.com") %>