Ben Finney wrote:
> "John Machin" <[EMAIL PROTECTED]> writes:
>
>
>>A little more is unfortunately not enough. The best advice you got was
>>to use an existing e-mail address validator. The definition of a valid
>>e-mail address is complicated. You may care to check out "Mastering
>>Regular Expressions" by Jeffery Friedl. In the first edition, at least
>>(I haven't looked at the 2nd), he works through assembling a 4700+ byte
>>regex for validating e-mail addresses. Yes, that's 4KB. It's the best
>>advertisement for *not* using regexes for a task like that that I've
>>ever seen.
>
>
> The best advice I've seen when people ask "How do I validate whether
> an email address is valid?" was "Try sending mail to it".
>
That only applies if it's a likely-looking email address. If someone
asks me to send mail to "splurge.!#$%*&[EMAIL PROTECTED]><{}_)" I will
probably assume that it isn't worth my time trying.
If the email looks syntactically correct, *then* it's worth further
validation by trying a delivery attempt.
> It's both Pythonic, and truly the best way. If you actually want to
> confirm, don't try to validate it statically; *use* the email address,
> and check the result. Send an email to that address, and don't use it
> any further unless you get a reply saying "yes, this is the right
> address to use" from the recipient.
>
This is a rather scatter-shot approach. Many possibilities can be
properly eliminated by judicious lexical checks before delivery is
considered.
> The sending system's mail transport agent, not regular expressions,
> determines which part is the domain to send the mail to.
>
> The domain name system, not regular expressions, determines what
> domains are valid, and what host should receive mail for that domain.
>
> Most especially, the receiving mail system, not regular expressions,
> determines what local-parts are valid.
>
Nevertheless, I am *not* going to try delivery to (for example) a
non-local address that doesn't contain an "at@ sign.
regards
Steve
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