How to check whether email /domain exists

[Gustavo Cordova]

> 
> On a more serious note, about the only thing you can really do
> is to look up the MX record and see if the host it points to
> has an SMTP server by connecting to port 25.
> 

And after that sending the message to the intended recepient(s),
if the (supposed) smtp server replies with an error, then
you know that it *probably* doesn't exists (it may be misconfigured),
and if it replies with a success code, then it means that *maybe*
the address does exist, or the server is configured to just dump
any email to nonexistant addresses and ignore any errors.

So, in short, just send the message. You can't really know with
any degree of certainty beforehand if the address you're sending
to exists or not.

Salutations.

-gustavo