RE: Checking if email is valid
Yes, it would be nice if there was a syntax for sending a test message sort
of like an ACK that is not delivered to the recipient but merely results in
some status being sent back such as DELIVERABLE or NO SUCH USER or even
MAILBOX FULL.
An issue with the discussion that may be worth considering is that some
email addresses are not always valid or may not be valid yet but will be
activated later. If I plan on opening a business unit which DNS will later
support as specific.category.mycompany.com.au and we first want to write
some code and test it and roll everything out later, then a test for
u...@specific.category.mycompany.com.au could fail some tests now but may be
fine later. Or what if I turn my machine off on weekends and when it boots,
it sets up to be able to receive mail. Is the address only sometimes valid?
We cannot be sure what rules may change and for all we know, they will
select other UNICODE symbols to replace @ for use by countries not having an
@ on keyboards in the local language or support some syntax like {AT} to be
usable ...
I even wonder about a service along the lines of tinyurl where you register
a potentially long or complex or hard to type name and get a short readable
one instead that is just used to provide a re-direct or even changed
periodically to dynamically point to where you want them now, such for the
current day of the week. I can easily imagine them making a funny looking
email address such as user@TINYqwerty that may not pas your current test or
one that looks valid to you but maps into an invalid or even null address.
BTW, checking if an email is valid is much wider as a concept than whether
the email address looks like a possible address. A big check sometimes made
if if the headers in the message and various formatting issues look
reasonable or issues about attachments and even if it is passed by SPAM
detectors. This discussion is just about if an email address LOOKS possibly
valid or should not be accepted.
I note earlier iterations of email had addressed like
mach1!mach2!mach3!ihnp4!mach5!mach6!user or even mach1!mach2!user@mach3 and
I remember tools that analyzed what other machines various machines claimed
to have a direct connection to and tried to figure out a connection from
your source to destination, perhaps a shorter one or maybe a less expensive
one. Hence machines like ihnp4 and various universities that were densely
connected to others got lots of traffic. In that scenario, validity had
another meaning.
-Original Message-
From: Python-list On
Behalf Of D'Arcy Cain via Python-list
Sent: Wednesday, November 1, 2023 9:57 PM
To: python-list@python.org
Subject: Re: Checking if email is valid
On 2023-11-01 17:17, Chris Angelico via Python-list wrote:
> On Thu, 2 Nov 2023 at 08:09, Grant Edwards via Python-list
> wrote:
>> Make sure it has an '@' in it. Possibly require at least one '.'
>> after the '@'.
>
> No guarantee that there'll be a dot after the at. (Technically there's
> no guarantee of an at sign either, but email addresses without at
> signs are local-only, so in many contexts, you can assume there needs
> to be an at.)
druid!darcy - doesn't work any more but not because it is syntactically
incorrect.
Remember the good old days when we were able to test if an address
existed without sending? That was before the black hats discovered the
Internet.
--
D'Arcy J.M. Cain
System Administrator, Vex.Net
http://www.Vex.Net/ IM:da...@vex.net
VoIP: sip:da...@vex.net
--
https://mail.python.org/mailman/listinfo/python-list
--
https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
See https://www.linuxjournal.com/article/9585?page=0,0 On 01/11/2023 17:09, Simon Connah via Python-list wrote: Hi, I'm building a simple project using smtplib and have a question. I've been doing unit testing but I'm not sure how to check if an email message is valid. Using regex sounds like a bad idea to me and the other options I found required paying for third party services. Could someone push me in the right direction please? I just want to find out if a string is a valid email address. Thank you. Simon. -- Ian Hobson Tel (+66) 626 544 695 -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 2023-11-01 17:17, Chris Angelico via Python-list wrote: On Thu, 2 Nov 2023 at 08:09, Grant Edwards via Python-list wrote: Make sure it has an '@' in it. Possibly require at least one '.' after the '@'. No guarantee that there'll be a dot after the at. (Technically there's no guarantee of an at sign either, but email addresses without at signs are local-only, so in many contexts, you can assume there needs to be an at.) druid!darcy - doesn't work any more but not because it is syntactically incorrect. Remember the good old days when we were able to test if an address existed without sending? That was before the black hats discovered the Internet. -- D'Arcy J.M. Cain System Administrator, Vex.Net http://www.Vex.Net/ IM:da...@vex.net VoIP: sip:da...@vex.net -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 01Nov2023 14:08, Grant Edwards wrote: On 2023-11-01, Simon Connah via Python-list wrote: I'm building a simple project using smtplib and have a question. I've been doing unit testing but I'm not sure how to check if an email message is valid. [...] Could someone push me in the right direction please? I just want to find out if a string is a valid email address. I confess that I punt "syntactically valid" to email.utils.getaddresses: https://docs.python.org/3/library/email.utils.html#email.utils.getaddresses "Deliverable"? I'm prepared to just send to it and hope not to get a bounce; delivery of email is, after all, asynchronous. (Even if it were going direct to the primary MX, I still hand it to the local mail system to deal with.) "A real person or entity"? A lot of systems do the round trip thing: here's a special unique and opaue URL,please visit it to confirm receipt of this email (implying email is 'real"). You see this a lot when signing up for things. And for plenty of things I generate a random throw away address at mailinator.com (looking at you, every "catch up" free online TV streaming service who still wants me to log in). Cheers, Cameron Simpson -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 11/1/23 04:09, Simon Connah via Python-list wrote: > Hi, > > I'm building a simple project using smtplib and have a question. I've been > doing unit testing but I'm not sure how to check if an email message is > valid. Using regex sounds like a bad idea to me and the other options I found > required paying for third party services. > > Could someone push me in the right direction please? I just want to find out > if a string is a valid email address. If I had a nickle for every time a web site claimed my email address wasn't valid I'd be a rich person. Seems like most attempts at solving this little problem fall short! -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On Thu, 2 Nov 2023 at 08:52, Grant Edwards via Python-list wrote: > > On 2023-11-01, Chris Angelico via Python-list wrote: > > On Thu, 2 Nov 2023 at 08:09, Grant Edwards via Python-list > > wrote: > > >> Make sure it has an '@' in it. Possibly require at least one '.' > >> after the '@'. > > > > No guarantee that there'll be a dot after the at. > > Ah, I forgot about defaulting to a local domain if one is > omitted. Will MTAs do that these days? Yeah they will; but that'll depend on the exact server you send to, whereas if you have a domain part, all you need is some server that accepts mail for forwarding. > > (Technically there's no guarantee of an at sign either, but email > > addresses without at signs are local-only, so in many contexts, you > > can assume there needs to be an at.) > > > > So the regex to match all valid email addresses that aren't > > local-only is... drumroll please... > > > > r"@" > > Unless you want to support UUCP or X400 addresses... > > :) Yyyyeah I think we can assume SMTP these days :) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 2023-11-01, Chris Angelico via Python-list wrote: > On Thu, 2 Nov 2023 at 08:09, Grant Edwards via Python-list > wrote: >> Make sure it has an '@' in it. Possibly require at least one '.' >> after the '@'. > > No guarantee that there'll be a dot after the at. Ah, I forgot about defaulting to a local domain if one is omitted. Will MTAs do that these days? > (Technically there's no guarantee of an at sign either, but email > addresses without at signs are local-only, so in many contexts, you > can assume there needs to be an at.) > > So the regex to match all valid email addresses that aren't > local-only is... drumroll please... > > r"@" Unless you want to support UUCP or X400 addresses... :) -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On Thu, 2 Nov 2023 at 08:09, Grant Edwards via Python-list wrote: > Make sure it has an '@' in it. Possibly require at least one '.' > after the '@'. No guarantee that there'll be a dot after the at. (Technically there's no guarantee of an at sign either, but email addresses without at signs are local-only, so in many contexts, you can assume there needs to be an at.) So the regex to match all valid email addresses that aren't local-only is... drumroll please... r"@" ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 2023-11-01, Simon Connah via Python-list wrote: > I'm building a simple project using smtplib and have a > question. I've been doing unit testing but I'm not sure how to check > if an email message is valid. Send an e-mail using it? If the right person gets the e-mail, then it's valid? > Using regex sounds like a bad idea to me and the other options I > found required paying for third party services. > > Could someone push me in the right direction please? I just want to > find out if a string is a valid email address. You'll have to define "valid". Valid syntactically according to ? Will be accepted by an SMTP server somewhere? Corresponds to a real person? Make sure it has an '@' in it. Possibly require at least one '.' after the '@'. Trying to do anything more than that is just wasting your time and annoying the mule. -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 2023-11-01, Mats Wichmann wrote: > On 11/1/23 05:35, Simon Connah via Python-list wrote: >> OK. I've been doing some reading and that you should avoid regex to check >> email addresses. So what I was thinking was something like this: > > To be a little more specific, Avoid Rolling Your Own RegEx. It's very > tricky, and you will get it subtly wrong. Use e.g.: https://gitea.ksol.io/karolyi/py3-validate-email -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 02/11/2023 00.35, Simon Connah via Python-list wrote: OK. I've been doing some reading and that you should avoid regex to check email addresses. This operation used to be a BIG THING back in the days of 'everyone' building PHP web-sites. When there were only a handful of TLDs (top-level domain names, eg the country-codes* such as .nz and .uk plus the generics such as .com and .net. Accordingly, one could hold the entire list for convenience of checking. However when IANA (the outfit responsible for the Root Zone Database and especially ICANN realised that there was money to be made, they allowed more and more TLDs. Keeping-up became a rat-race! Indeed, I've held another .info domain for twenty years, and used to suffer for my 'bleeding edge' daring - quite recently someone (who should remain name-less, and a few other less-es) sent me an email telling me how to log-in, but their log-in process wouldn't accept the 'illegal' address. Um... All together now: "a little bit of knowledge is a dangerous thing"! So what I was thinking was something like this: if type(email_recipient) != email.message.Message: I just don't know why that particular line isn't working. Will need more context. What is the objective? What is the source/pre-processing of these data-items. (etc) * Left-out .au, (a less important geo-TLD) to wind-up @Chris... -- Regards, =dn -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 11/1/23 05:35, Simon Connah via Python-list wrote: OK. I've been doing some reading and that you should avoid regex to check email addresses. So what I was thinking was something like this: To be a little more specific, Avoid Rolling Your Own RegEx. It's very tricky, and you will get it subtly wrong. All depending, as others have said, on what level of "validation" you're after. -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On Thu, 2 Nov 2023 at 06:02, Jon Ribbens via Python-list wrote: > > On 2023-11-01, Chris Angelico wrote: > > On Thu, 2 Nov 2023 at 05:21, Simon Connah via Python-list > > wrote: > >> Could someone push me in the right direction please? I just want to > >> find out if a string is a valid email address. > > > > There is only one way to know that a string is a valid email address, > > and that's to send an email to it. > > > > What is your goal though? For example, if you're trying to autolink > > email addresses in text, you don't really care whether it's valid, > > only that it looks like an address. > > There's often value in even only partially-effective checks though. > With an email address you can easily check to see if it has an "@", > and if the stuff after the "@" is a syntactically valid domain name. > You can also go a bit further and check to see if the domain has an > MX record, and if it doesn't then it is extremely unlikely that the > address is valid. Yeah, which is why I asked about the goal. (You may also note that I worded the prior statement very carefully: You cannot know that it IS valid without sending email to it, but there can be ways to know that it CANNOT BE valid.) In the vast majority of contexts, local addresses can be ignored, so an email address will have to include an at sign. I wouldn't bother with a syntax check on the domain portion, though; just check for a couple of possible formats (IP literal), and if it looks like a domain name, do the MX lookup. That said, though, there are certain contexts where you can be a LOT more restrictive, such as the autolinking example I mentioned; it's fine to exclude some unusual email addresses when all you're doing is offering a small convenience. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On 2023-11-01, Chris Angelico wrote: > On Thu, 2 Nov 2023 at 05:21, Simon Connah via Python-list > wrote: >> Could someone push me in the right direction please? I just want to >> find out if a string is a valid email address. > > There is only one way to know that a string is a valid email address, > and that's to send an email to it. > > What is your goal though? For example, if you're trying to autolink > email addresses in text, you don't really care whether it's valid, > only that it looks like an address. There's often value in even only partially-effective checks though. With an email address you can easily check to see if it has an "@", and if the stuff after the "@" is a syntactically valid domain name. You can also go a bit further and check to see if the domain has an MX record, and if it doesn't then it is extremely unlikely that the address is valid. -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
On Thu, 2 Nov 2023 at 05:21, Simon Connah via Python-list wrote: > > Could someone push me in the right direction please? I just want to find out > if a string is a valid email address. There is only one way to know that a string is a valid email address, and that's to send an email to it. What is your goal though? For example, if you're trying to autolink email addresses in text, you don't really care whether it's valid, only that it looks like an address. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Checking if email is valid
Hi, I'm building a simple project using smtplib and have a question. I've been doing unit testing but I'm not sure how to check if an email message is valid. Using regex sounds like a bad idea to me and the other options I found required paying for third party services. Could someone push me in the right direction please? I just want to find out if a string is a valid email address. Thank you. Simon. signature.asc Description: OpenPGP digital signature -- https://mail.python.org/mailman/listinfo/python-list
Re: Checking if email is valid
OK. I've been doing some reading and that you should avoid regex to check email addresses. So what I was thinking was something like this: if type(email_recipient) != email.message.Message: I just don't know why that particular line isn't working. Thank you! --- Original Message --- On Wednesday, 1 November 2023 at 10:09, Simon Connah wrote: > > > Hi, > > I'm building a simple project using smtplib and have a question. I've been > doing unit testing but I'm not sure how to check if an email message is > valid. Using regex sounds like a bad idea to me and the other options I found > required paying for third party services. > > Could someone push me in the right direction please? I just want to find out > if a string is a valid email address. > > Thank you. > > Simon. signature.asc Description: OpenPGP digital signature -- https://mail.python.org/mailman/listinfo/python-list
