ASP Program to validate email address

This is a simple ASP Program to validate email address. The IsValidEmail() function checks for a valid email and returns true if the email address is a valid email otherwise it returns false if the email address isn’t proper syntax. The code is well commented and should explain what is happening .

This code checks for @ and a . period sign as well as only acceptable characters. i.e. if a user have entered # or $ sign in his/her email address then this function will return false.

'*******************************************************
'* MYCPLUS Sample Code - https://www.mycplus.com *
'* *
'* This code is made available as a service to our *
'* visitors and is provided strictly for the *
'* purpose of illustration. *
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'* Please direct all inquiries to saqib at mycplus.com *
'*******************************************************

Function IsValidEmail(emailAddress)
'Declare variables
Dim ValidEmail, emailParts, iLoopCounter, emailChar, acceptableChars
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 the last & 2nd character from right part using Right function
If Right(emailParts(1), 1) = "." OR Right(emailParts(1), 2) = "." 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 '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