[dba-Tech] Verifying Accuracy or Legitimacy of Email Address

On 12 Dec 2004 at 12:58, Arthur Fuller wrote:

> I have a web page upon which I request the user's email address. 

The important qestion here is: Why? 

>What I 
> have in mind is that the moment the user tabs out of this textbox, I 
> immediately send a test message to said address to see if it's at least 
> real. (It may be real but inaccurate and there's not much I can think of 
> to get around that problem, so let's just deal with the "real" problem.)
> 

Email is not an instance messaging medium.  There can be all sorts of 
delays in message delivery for any number of reasons,. The minimum 
recommended  timeouts for the various transactions in a mail delivery vary 
between 2 and 10 minutes including a 5 minute timeout on the initial 
connection.  In other words, a single mail transaction can take up to an 
hour to complete   Most SMTP servers will retry for several daya to deliver 
a message if they receive a 400 series delivery failure.  

> 3. Is there any way to detect whether the bounce was caused by a bad 
> address or alternatively by a spam-blocker etc.? 

If the email address is to a vaild SMTP server, the receiving SMTP server 
will return a numeric code to the originating SMTP server (not to your ASP 
page)

> And supposing that I 
> could detect the latter, what sort of advice could I offer the visitor 
> to allow my mail in? I guess I would have to know the particular blocker 
> in use, etc., which is a nested can of worms I don't really want to get 
> into.
> 
> Any advice?

Rethink the whole concept. Unless you are going to email instructions to 
the viewer (such as a password to proceed further) you are wasting your 
time.  Unless there is a valid reason for supplying a true email address , 
you will find that most of your logins are from wgates at microsoft.com :-)

-- 
Stuart