6 ms·

I maintain that the only reasonable way to validate an email address is to send it a message and hope for a reply. Every other method I've ever tried has failed

I maintain that the only reasonable way to validate an email address is to send it a message and hope for a reply. Every other method I've ever tried has failed in some silly way, as described in the article.

SamReidHughes 6y ago
Sometimes you need to harvest email addresses and want to distinguish them from junk data. If you're actually developing the algorithm in the face of real data, you'll get a good validator.
dgellow 6y ago
Yep, I agree. On frontend, use a very simple validation such as /.+@.+\..+/ (better to use string splits IMHO, but you see the idea) just to give users some feedbacks in case of a clearly invalid email. On the backend send an email and let the user confirms.
geoelectric 6y ago
As far as I know, that literally is the only way to validate an email address, universally speaking, beyond an internal whitespace check. But I think if you take "local" out of the equation, as you would for customer emails, you can validate a bit more. You might be able to validate on a single @ being in there somewhere, with something before and after it, maybe look for a period after the @ for "addr@domain.tld" as I think every external address needs a dotted domain. That's about as far as I think you can safely go. Anything else is legal.
- arp242 6y ago
  Domains labels are fairly strictly defined, so you check that a bit more stringently. > as I think every external address needs a dotted domain. Something like example@com is technically a valid email address; although I don't know if there are any TLDs which accept emails.
  - geoelectric 6y ago
    That's true, I didn't think about that case. I don't think I've ever seen a bare TLD in real life like that though--maybe very early on as DNS became a thing? Not since the web though.
- sohex 6y ago
  Well, maybe not a single @. At least one @ maybe. There's a set of special characters that aren't permitted in the local part of an email address including @... unless they're quoted. So "@"@example.com is a valid address.
  - geoelectric 6y ago
    Oof, thanks. I forgot you could quote the @ and thought it was the one universally illegal character. Also forgot there were others, oops. I usually just recommend people don't validate email addys and let the email verification message do the job for you. This is pretty much why.

SamReidHughes 6y ago

Sometimes you need to harvest email addresses and want to distinguish them from junk data. If you're actually developing the algorithm in the face of real data, you'll get a good validator.

dgellow 6y ago

Yep, I agree. On frontend, use a very simple validation such as /.+@.+\..+/ (better to use string splits IMHO, but you see the idea) just to give users some feedbacks in case of a clearly invalid email. On the backend send an email and let the user confirms.

geoelectric 6y ago

As far as I know, that literally is the only way to validate an email address, universally speaking, beyond an internal whitespace check. But I think if you take "local" out of the equation, as you would for customer emails, you can validate a bit more. You might be able to validate on a single @ being in there somewhere, with something before and after it, maybe look for a period after the @ for "addr@domain.tld" as I think every external address needs a dotted domain. That's about as far as I think you can safely go. Anything else is legal.

arp242 6y ago
Domains labels are fairly strictly defined, so you check that a bit more stringently. > as I think every external address needs a dotted domain. Something like example@com is technically a valid email address; although I don't know if there are any TLDs which accept emails.
- geoelectric 6y ago
  That's true, I didn't think about that case. I don't think I've ever seen a bare TLD in real life like that though--maybe very early on as DNS became a thing? Not since the web though.
sohex 6y ago
Well, maybe not a single @. At least one @ maybe. There's a set of special characters that aren't permitted in the local part of an email address including @... unless they're quoted. So "@"@example.com is a valid address.
- geoelectric 6y ago
  Oof, thanks. I forgot you could quote the @ and thought it was the one universally illegal character. Also forgot there were others, oops. I usually just recommend people don't validate email addys and let the email verification message do the job for you. This is pretty much why.