Four kinds of ASP e-mail verification functions

Public Function Isemail (ByVal pstring)
Dim plt,pgt:plt = FALSE:PGT = False
For x = 2 to Len (pstring)-1
If Mid (pstring,x,1) = "@" Then Plt = True
If Mid (pstring,x,1) = "." and Plt = True Then PGT = True
Next
If Plt = True and PGT = True Then
Isemail = True
Else
Isemail = False
End If
End Function
%>

'********************************************
' Function name: IsValidEmail
' Function: check email address legality
' Parameters: Email----email address to check
' Return value: True----Email address is valid
' False----Email address is illegal
'********************************************

Public Function IsValidEmail (Email)
Dim names, name, I, C
IsValidEmail = True
Names = Split (Email, "@")
If UBound (names) <> 1 Then isvalidemail = False:exit Function
For each name in names
If Len (name) <= 0 Then isvalidemail = false:exit Function
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
Next
If Left (name, 1) = "." Or Right (name, 1) = "." Then IsValidEmail = False:exit Function
Next
If InStr (Names (1), ".") <= 0 Then isvalidemail = false:exit Function
I = Len (names (1))-InStrRev (names (1), ".")
If I <> 2 and I <> 3 Then isvalidemail = False:exit Function
If InStr (Email, "...") > 0 Then isvalidemail = False
End Function

<%
Function Isemail (STRNG)
Isemail = False
Dim RegEx, Match
Set regEx = New RegExp
Regex.pattern = "^w+" (-w+) | (. w+)) *@[a-za-z0-9]+ ((. | -) [a-za-z0-9]+] *. [a-za-z0-9]+$]
Regex.ignorecase = True
Set Match = Regex.execute (strng)
If Match.count then isemail= true
End Function
%>

Public

Function Chkmail (ByVal Email)
Dim Rep,pmail:chkmail = True:set Rep = New RegExp
Rep.pattern = "([. a-za-z0-9_-]) {2,10}@ ([a-za-z0-9_-]) {2,10} (.) ( [A-za-z0-9]) {2,}) {1,4}$ "
Pmail = Rep.test (Email): Set Rep = Nothing
If not pmail Then chkmail = False
End Function