Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Email Regex that works 99.99%

emailregex.com

Post reply on HN
Print view View original

21–30 of 65 posts

Re: Email Regex that works 99.99%

#21

Post by falcolas »

After extensive research, I have finally come up with a way to improve upon 99.99%. I have come up with a regex which will work for 100% of email addresses, and a significant number of regex engines, as an added bonus! Behold:

    .*@.*
/s

Re: Email Regex that works 99.99%

#22

Post by chrisfarms »

Yeah this is not great practice.

We built an app where sending a validation email upfront was not a practical option some time ago, and the best strategy I found for ensuring the email was valid was to lookup the MX records and ask the mailserver for the given domain, by issuing RCPT commands. Many mailservers will just drop connections when RCPT is for someone who doesn't exist or can't be routed to which was a good indicator of a typo or invalid address. And of course if the MX lookup fails the domain is incorrect.

Still wouldn't recommend this method either though really.

Re: Email Regex that works 99.99%

#23

Post by wtbob »

bshimmin wrote: post #5

Utterly pointless. An email regex tells you that the email address (probably) conforms to a pattern that means it might be a valid email address (for now, until new weird TLDs emerge and the patterns have to change...), but it has no way of telling you whether that address can actually receive mail. `foo@bar` fails these regular expressions and `foo@bar.invalid` passes them, but neither will receive mail. As I have t…

> `foo@bar` fails these regular expressions and `foo@bar.invalid` passes them, but neither will receive mail.

foo@bar could still receive email, if you had a host in your DNS domain named bar, with a user named foo.

Re: Email Regex that works 99.99%

#24

Post by fphilipe »

falcolas wrote: post #21

After extensive research, I have finally come up with a way to improve upon 99.99%. I have come up with a regex which will work for 100% of email addresses, and a significant number of regex engines, as an added bonus! Behold: .*@.* /s

    .+@.+
Should do the trick

Re: Email Regex that works 99.99%

#27

Post by Piskvorrr »

ThePadawan wrote: post #26
imron wrote: post #25

So in 1 million emails, there are 10,000 valid emails that will be rejected. I guess if you use this regex then you'd better hope your service doesn't become popular.

Your math is off by a factor of 100.

Assuming that the 99.99 figure is not something the author pulled out of...thin air. In absence of any data, I'm inclined to believe that the figure was gained by this very method.

Edit: Oh look, the submitter has pulled yet another figure out of thin air (author says "three nines, trust me," submitter says "four nines, omgwtfbetterthanslicedbread!!!1!"). Suspiciouser and suspiciouser.

Re: Email Regex that works 99.99%

#29

Post by falcolas »

fphilipe wrote: post #24
falcolas wrote: post #21

After extensive research, I have finally come up with a way to improve upon 99.99%. I have come up with a regex which will work for 100% of email addresses, and a significant number of regex engines, as an added bonus! Behold: .*@.* /s

.+@.+ Should do the trick

I considered that one, but I'm sure there's some system out there which doesn't require an account name ahead of the "@" symbol. We're shooting for 100% accuracy, after all. ;)
Post reply on HN