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