Validating EMailAdresses for syntactical correctness
Michael W. Dietrich
validates EMail-Addresses (e.g. such entered in Web Forms) for their
syntactical correctness? If so, is that algorithm available? Where?
Any comments on this matter are appreciated.
regards
Michael
Mark McEahern
> Has anyone ever written a class, function or regular expression, that
> validates EMail-Addresses (e.g. such entered in Web Forms) for their
> syntactical correctness? If so, is that algorithm available? Where?
Hmm, have you tried google? There may not be such in Python, but I'm sure
you can translate whatever samples you find. The basic idea is to use
regular expressions, right? I remember seeing an approach that explicitly
provided different levels of strictness. Something like this:
Level 1: Just make sure you have something@something
Level 2: Make sure you have some...@something.something
Level 3: Make sure the tld is valid.
Level 4: Make sure the domain is valid (whois, ping, etc)
Level 5: Make sure the address itself is valid (resolve the mx record and
test the address via smtp).
Cheers,
// mark
Cameron Laird
> .
> .
... and even then, there are no guarantees. You can go all
the way through Level 5, and *still* find a bogus address
on your hands. Make sure your customer/client/supervisor
understands that.
E-mail connectivity is only weakly about syntax, despite the
eagerness of many practitioners to show off their REs.
--
Cameron Laird <Cam...@Lairds.com>
Business: http://www.Phaseit.net
Personal: http://starbase.neosoft.com/~claird/home.html
Mark McEahern
> ... and even then, there are no guarantees. You can go all
> the way through Level 5, and *still* find a bogus address
> on your hands. Make sure your customer/client/supervisor
> understands that.
>
> E-mail connectivity is only weakly about syntax, despite the
> eagerness of many practitioners to show off their REs.
Yeah, I should have mentioned that my own personal preference is to avoid
all this RE-based validation crap and just generate an email to the supplied
address that contains a URL that when navigated to confirms the validity of
the address.
That's much more straightforward, imho, and avoids all this, "What are the
valid tld's?" mess. Just take whatever the user supplies and send them a
confirmation email.
But, to each his own,
Cheers,
// mark
Krasna Halopti
I agree with all the other replies to your post about the caveats on
validation. However, I have found some uses, e.g. client-side
validation in forms to catch user typos. In Javascript, I have used
the re.
"^\\w(\\w|\\.\\w)*@\\w(\\w|\\.\\w)*$"
I have not tested this in Python but it should need only minor mods,
if any...since you mention Web forms in your post, it may be that you
can do this browser-side.
Hope this helps
Erno Kuusela
| I remember seeing an approach that explicitly
| provided different levels of strictness. Something like this:
| Level 1: Just make sure you have something@something
| Level 2: Make sure you have some...@something.something
"user@com." is (syntactically) valid too, i think.
| Level 3: Make sure the tld is valid.
| Level 4: Make sure the domain is valid (whois, ping, etc)
it can be hard to keep track of all the whois servers for all tld's.
| Level 5: Make sure the address itself is valid (resolve the mx record and
| test the address via smtp).
transient network problems can bite you here (also applies to 4).
-- erno
Jason Voegele
If you really want to ensure 100% syntactical correctness, here's the
regular expression for matching email addresses, from Jeffrey Friedl's
"Mastering Regular Expressions" book ;-)
[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\
xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xf
f\n\015()]*)*\)[\040\t]*)*(?:(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\x
ff]+(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff])|"[^\\\x80-\xff\n\015
"]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015"]*)*")[\040\t]*(?:\([^\\\x80-\
xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80
-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*
)*(?:\.[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\
\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\
x80-\xff\n\015()]*)*\)[\040\t]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x8
0-\xff]+(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff])|"[^\\\x80-\xff\n
\015"]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015"]*)*")[\040\t]*(?:\([^\\\x
80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^
\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040
\t]*)*)*@[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([
^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\
\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\
x80-\xff]+(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff])|\[(?:[^\\\x80-
\xff\n\015\[\]]|\\[^\x80-\xff])*\])[\040\t]*(?:\([^\\\x80-\xff\n\015()
]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\
x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:\.[\04
0\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\
n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\
015()]*)*\)[\040\t]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?!
[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff])|\[(?:[^\\\x80-\xff\n\015\[\
]]|\\[^\x80-\xff])*\])[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\
x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\01
5()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*)*|(?:[^(\040)<>@,;:".
\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]
)|"[^\\\x80-\xff\n\015"]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015"]*)*")[^
()<>@,;:".\\\[\]\x80-\xff\000-\010\012-\037]*(?:(?:\([^\\\x80-\xff\n\0
15()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][
^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)|"[^\\\x80-\xff\
n\015"]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015"]*)*")[^()<>@,;:".\\\[\]\
x80-\xff\000-\010\012-\037]*)*<[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?
:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-
\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:@[\040\t]*
(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015
()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()
]*)*\)[\040\t]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\0
40)<>@,;:".\\\[\]\000-\037\x80-\xff])|\[(?:[^\\\x80-\xff\n\015\[\]]|\\
[^\x80-\xff])*\])[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\
xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*
)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:\.[\040\t]*(?:\([^\\\x80
-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x
80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t
]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\
\[\]\000-\037\x80-\xff])|\[(?:[^\\\x80-\xff\n\015\[\]]|\\[^\x80-\xff])
*\])[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x
80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80
-\xff\n\015()]*)*\)[\040\t]*)*)*(?:,[\040\t]*(?:\([^\\\x80-\xff\n\015(
)]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\
\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*@[\040\t
]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\0
15()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015
()]*)*\)[\040\t]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(
\040)<>@,;:".\\\[\]\000-\037\x80-\xff])|\[(?:[^\\\x80-\xff\n\015\[\]]|
\\[^\x80-\xff])*\])[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80
-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()
]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:\.[\040\t]*(?:\([^\\\x
80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^
\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040
\t]*)*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".
\\\[\]\000-\037\x80-\xff])|\[(?:[^\\\x80-\xff\n\015\[\]]|\\[^\x80-\xff
])*\])[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\
\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x
80-\xff\n\015()]*)*\)[\040\t]*)*)*)*:[\040\t]*(?:\([^\\\x80-\xff\n\015
()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\
\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*)?(?:[^
(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\[\]\000-
\037\x80-\xff])|"[^\\\x80-\xff\n\015"]*(?:\\[^\x80-\xff][^\\\x80-\xff\
n\015"]*)*")[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|
\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))
[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:\.[\040\t]*(?:\([^\\\x80-\xff
\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\x
ff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(
?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\[\]\
000-\037\x80-\xff])|"[^\\\x80-\xff\n\015"]*(?:\\[^\x80-\xff][^\\\x80-\
xff\n\015"]*)*")[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\x
ff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)
*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*)*@[\040\t]*(?:\([^\\\x80-\x
ff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-
\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)
*(?:[^(\040)<>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\[\
]\000-\037\x80-\xff])|\[(?:[^\\\x80-\xff\n\015\[\]]|\\[^\x80-\xff])*\]
)[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-
\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\x
ff\n\015()]*)*\)[\040\t]*)*(?:\.[\040\t]*(?:\([^\\\x80-\xff\n\015()]*(
?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]*(?:\\[^\x80-\xff][^\\\x80
-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)*\)[\040\t]*)*(?:[^(\040)<
>@,;:".\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\[\]\000-\037\x8
0-\xff])|\[(?:[^\\\x80-\xff\n\015\[\]]|\\[^\x80-\xff])*\])[\040\t]*(?:
\([^\\\x80-\xff\n\015()]*(?:(?:\\[^\x80-\xff]|\([^\\\x80-\xff\n\015()]
*(?:\\[^\x80-\xff][^\\\x80-\xff\n\015()]*)*\))[^\\\x80-\xff\n\015()]*)
*\)[\040\t]*)*)*>)
Jason Voegele
Cameron Laird
Jason Voegele <ja...@jvoegele.com> wrote:
> ...
>If you really want to ensure 100% syntactical correctness, here's the
>regular expression for matching email addresses, from Jeffrey Friedl's
>"Mastering Regular Expressions" book ;-)
Jason, please! You really should post warnings in
such follow-ups; there might be children or other
tender minds present.
Steve Holden
> > Has anyone ever written a class, function or regular expression, that
> > validates EMail-Addresses (e.g. such entered in Web Forms) for their
> > syntactical correctness? If so, is that algorithm available? Where?
> >
> > Any comments on this matter are appreciated.
>
> If you really want to ensure 100% syntactical correctness, here's the
> regular expression for matching email addresses, from Jeffrey Friedl's
> "Mastering Regular Expressions" book ;-)
>
>
I trust this expression is accompanied by a proof of correctness in the
book.
regards
Steve
--
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Python Web Programming: http://pydish.holdenweb.com/pwp/
Pete Shinners
> If you really want to ensure 100% syntactical correctness, here's the
> regular expression for matching email addresses, from Jeffrey Friedl's
> "Mastering Regular Expressions" book ;-)
>
<< MIME encoded re-sample deleted :] >>
any summary on what that's supposed to mean?
(beyond "validate email address")
Aahz Maruch
Pete Shinners <pe...@shinners.org> wrote:
>Jason Voegele wrote:
>>
>> If you really want to ensure 100% syntactical correctness, here's the
>> regular expression for matching email addresses, from Jeffrey Friedl's
>> "Mastering Regular Expressions" book ;-)
>
><< MIME encoded re-sample deleted :] >>
I see you've got a smiley, but just in case anyone is lacking in
attention, the regex was *not* MIME encoded.
>any summary on what that's supposed to mean?
>(beyond "validate email address")
Read the Friedl book. Seriously.
--
--- Aahz <*> (Copyright 2002 by aa...@pobox.com)
Hugs and backrubs -- I break Rule 6 http://www.rahul.net/aahz/
Androgynous poly kinky vanilla queer het Pythonista
"I support family values -- Addams family values" --www.nancybuttons.com
Branimir Petrovic
"Michael W. Dietrich" <Michael.W...@modulo3.de> wrote in message news:54da4e24.02012...@posting.google.com...
> Has anyone ever written a class, function or regular expression, that
> validates EMail-Addresses (e.g. such entered in Web Forms) for their
> syntactical correctness? If so, is that algorithm available? Where?
>
Email validation is a tricky business. "Algorithm" is called RFC 2822
(see http://rfc.net/rfc2822.html). Be warned to set aside enough time
to go to the bottom. Once there (@theBottom) you'll probably realize
that proper testing/checking is just not worthwhile. Even though all
looks and feels right, the very first part (before @ char) may contain
unintentional (spelling) error and as a result - mail will never reach
the recipient...
One of many possible ways to tackle the problem:
http://www.serialscripter.com/scripts/EMailValidatorCLS.html
(JScript)
Branimir
Alexander Skwar
> Has anyone ever written a class, function or regular expression, that
> validates EMail-Addresses (e.g. such entered in Web Forms) for their
> syntactical correctness? If so, is that algorithm available? Where?
Forget it. Although there are some "rules" defined by the RFCs about
how the localpart (before the @) should look like, in reality you'll
find that close to every character can appear there. I'm just starting
with Python, but in PHP based apps, I resorted to simply checking if
there's a MX (mail exchange) server listed for the domain. If that
returns true, then all is fine.
Alexander Skwar
--
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Alexander Skwar
> Level 5: Make sure the address itself is valid (resolve the mx record and
> test the address via smtp).
This won't work. A lot of the huge providers (AOL, T-Online...) always
give a true result here, even if the adress does not exist. This is
also done for anti-spam measures, because if a spammer could so easily
check if a given adress exists, it would help him.
Alexander Skwar
--
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Alexander Skwar
> validation. However, I have found some uses, e.g. client-side
> validation in forms to catch user typos. In Javascript, I have used
What's a "typo"? Suppose I'd be using Lotus Notes, then my adress could
actually look like "Alexander.Skwar/some/where@domain". This would
resolve to a typo in your case, although that adress is valid.
> if any...since you mention Web forms in your post, it may be that you
> can do this browser-side.
Never do this! If you rely on something client-side for checks, you're
in hell, because disabling JavaScript iwll break the check, and forging
the reply sent by the browser is very easy.
Alexander Skwar
--
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Cameron Laird
Alexander Skwar <ASk...@DigitalProjects.com> wrote:
>So sprach =BBMark McEahern=AB am 2002-01-24 um 10:26:36 -0800 :
>> Level 5: Make sure the address itself is valid (resolve the mx record and
>> test the address via smtp).
>
>This won't work. A lot of the huge providers (AOL, T-Online...) always
>give a true result here, even if the adress does not exist. This is
>also done for anti-spam measures, because if a spammer could so easily
>check if a given adress exists, it would help him.
... and, as someone else posted, even if MX resolves
to an address that is unreachable, that doesn't mean
the address is necessarily wrong--it could just be
temporarily off-line.
Doobee R. Tzeck
It is able to validate all valid RfC 822 Addresses like
Muhammed.(I am the greatest) Ali @(the)Vegas.WBA
"\"quote.and space"@[].[\[].yp.to (Might work)
<@gateway.af.mil:Go...@heaven.af.mil>
<mailto:@c0re.jp>
this are all valid addresses. RfC 822 address parsing -which is
the essential for finding "valid" addresses is sheer horror.
drt
--
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me - http://koeln.ccc.de/~drt/
Grant Edwards
> It is able to validate all valid RfC 822 Addresses like
>
> Muhammed.(I am the greatest) Ali @(the)Vegas.WBA
> "\"quote.and space"@[].[\[].yp.to (Might work)
><@gateway.af.mil:Go...@heaven.af.mil>
><mailto:@c0re.jp>
>
> this are all valid addresses. RfC 822 address parsing -which is
> the essential for finding "valid" addresses is sheer horror.
It could be worse. You could have to parse addresses with mixed
822 and uucp bang notation (and it's various offspring).
Anyway, the correlation between being a "valid" 822 address and
whether mail sent to that address will end up anywhere useful
is probably small enough that it's not worth the effort.
--
Grant Edwards grante Yow! The Osmonds! You are
at all Osmonds!! Throwing up
visi.com on a freeway at dawn!!!
Cameron Laird
Michael W. Dietrich <Michael.W...@modulo3.de> wrote:
>Has anyone ever written a class, function or regular expression, that
>validates EMail-Addresses (e.g. such entered in Web Forms) for their
>syntactical correctness? If so, is that algorithm available? Where?
.
.
<URL: http://www.nist.gov/msidlibrary/doc/libes96b.ps >
specifically addresses address authentication.