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

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

1. How would I code that on a classic ASP page?
2. How would said page know if the mail bounced?
3. Is there any way to detect whether the bounce was caused by a bad 
address or alternatively by a spam-blocker etc.? 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?
Arthur



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