Member Avatar for BoogyB

i can't find a good code to check if e-mail exists. im trying to do this with cdo. maybe someone could sugest some source?
or maybe could help to make it...
here is what im trying to do

<%
Dim iMsg
Dim iConf
Dim Flds
Dim strHTML
set imsg = createobject("cdo.message")
set iconf = createobject("cdo.configuration")
Set Flds = iconf.Fields
With Flds
.Item("") = 2
.Item("") = "<SMTP Server>"
.Update
End With
strHTML = "<HTML>"
strHTML = strHTML & "<HEAD>"
strHTML = strHTML & "<BODY>"
strHTML = strHTML & "<b> This is the test HTML message body</b></br>"
strHTML = strHTML & "<hr>"
strHTML = strHTML & "This another section of the message...</BR>"
strHTML = strHTML & "</BODY>"
strHTML = strHTML & "</HTML>"
With iMsg Set
.Configuration = iConf
.To = "<valid e-mail address>"
.From = "<valid e-mail address>"
.Subject = "This is a test CDOSYS message (Setting DSN options)"
.HTMLBody = strHTML
.fields("urn:schemas:mailheader:disposition-notification-to") = "<valid e-mail address>"
.fields("urn:schemas:mailheader:return-receipt-to") = "<valid e-mail address>"
.DSNOptions = cdoDSNSuccessFailOrDelay
.DSNOptions = 14
.fields.update
.Send
End With

i'm sending message to the e-mail i want to check for validation. and i can get confirmation that mail was sent succesfuly. but the problem is that i get it by mail. i want to check if e-mail is valid in the source code. if its possible

thank you

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  • Latest Post Latest Post by Drew

Dani AI

Generated

Short answer: there is no foolproof, server‑side way in Classic ASP to prove an address "exists." 's CDO send produced a bounce message later because many MTAs accept mail during the SMTP session and generate DSNs asynchronously; only when the recipient server rejects at the RCPT stage will a synchronous error be available. 's whois suggestion checks domain registration but is weaker than a DNS/MX check for mail routing.

A practical, layered approach that balances reliability and safety:

  • Step 1 — syntactic check: fast client/server regex to reject obviously invalid addresses. Example VBScript (Classic ASP) for format checking:
Function IsValidEmail(addr)
  Dim re
  Set re = New RegExp
  re.Pattern = "^[A-Za-z0-9._%+\-]+@[A-Za-z0-9.\-]+\.[A-Za-z]{2,}$"
  re.IgnoreCase = True
  IsValidEmail = re.Test(addr)
End Function

  • Step 2 — DNS/MX lookup: confirm the domain has MX (or A) records. Classic ASP has no built‑in DNS API, so many people call nslookup via WScript.Shell or use a small native DLL/service to get MX hosts. Beware of server permissions when invoking shell commands.

  • Step 3 — SMTP RCPT probe (optional, fragile): open a TCP connection to the domain's MX on port 25 and run an EHLO/MAIL FROM/RCPT TO sequence. A 250 on RCPT TO suggests the server accepted the recipient; 550 or similar indicates rejection. Example SMTP reply flow:

220 mx.example.com ESMTP
EHLO validator.example.com
250 mx.example.com
MAIL FROM:<validator@domain.com>
250 OK
RCPT TO:<target@domain.com>
250 OK   <-- accepted  OR  550 No such user <-- rejected

Caveats: many servers accept everything (catch‑all), use greylisting, or silently defer bounces; probing can trigger rate limits or blacklistings. For reliable production validation the recommended, industry‑standard solution is an explicit confirmation email containing a unique activation link. For bulk or real‑time needs, third‑party validation services exist (they combine MX checks, SMTP probes and historical data) but carry cost and privacy considerations.

Recommended Answers

All 3 Replies

Member Avatar for Drew

There is no way to check that a email address exists in ASP. The only thing you could do is a "whois" on the domain to make sure it is real, but that is about all you can do.

Member Avatar for BoogyB

could you shoe an example of this?

Member Avatar for Drew

I can never actually needed to code this but you could probably take a look at this and recode it so check for the email domain of the user and make sure it is valid.

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