RE: Editing E-Mail Addresses

>If you can't locate the mx, the address is no good.

Actually this went around the list a month or two ago. IIRC, you check
for an MX record first. If it exists you MUST use it. If is doesn't
exist, you SHOULD check for an A record w/the domain name. If it exists
you use it. If no A record exists then you're toast.

-Walden 


------------
Walden H Leverich III
Tech Software
(516) 627-3800 x3051
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Rich Duzenbury
Sent: Monday, February 13, 2006 10:59 AM
To: RPG programming on the AS400 / iSeries
Subject: Re: Editing E-Mail Addresses

On Mon, 2006-02-13 at 10:42 -0500, Fisher, Don wrote:
> I'm creating a function to determine if an e-mail address is 
> syntactically correct and that its domain can handle e-mail.  I found 
> Scott Klement's excellent code for this at the following link:
> http://www.iseriesnetwork.com/resources/clubtech/index.cfm?fuseaction=
> ShowNe
> wsletterIssue&ID=17632
> 
> I've noticed, however, that this function assumes a domain name is 
> okay if it exists, even though it may not be able to handle e-mail.  
> An example is test.com, where the e-mail addresses are actually
testcentral.com.
> Presumably, mail sent to the test.com address would be rejected.
> 
> I modified the code slightly to always search for a mail exchanger and

> that seems to work except for our own domain (roomstore.com).
> 
> Would one of you kind folks set me straight as to how this stuff is 
> supposed to work?  I'm obviously not understanding this very well.
> 
This might help:

http://www.dnsstuff.com/tools/mail.ch?domain=dfisher%40roomstore.com

I think the steps are:

Locate mail exchanger IP's via the DNS records If you can't locate the
mx, the address is no good.

Contact mail exchanger(s) on smtp port.
If you can't connect, the address is suspect, but may still be good as
the mail exchanger may be down.

That's as far as you can go, practically speaking.  You could try to
send a mail to the address.  Some mail servers will reject unknown users
at the gateway, but other ones don't as a security measure, and you
won't be able to tell which don't.

The only way to know for sure it to actually send an e-mail to the
address and have the user click a specially designed link.  The special
link embeds enough data in it so you can go back to your database and
mark the e-mail address as valid.

Since you've subscribed to this mailing list, you've already been
through such a process from the user side.

HTH

Regards,
Rich

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