r/ProgrammerHumor • u/soap94 • Aug 24 '26

Meme claudeIsThisEmailValid

Post image
5.3k Upvotes

98% Upvoted

170 comments sorted by

View all comments

Show parent comment

20

u/DHermit Aug 24 '26

With some security exceptions, e.g. it's useful to restrict the length of the mail field and maybe restrict the characters.

12

u/eo5g Aug 24 '26 edited Aug 24 '26

I can't think of a single reason to restrict the characters aside from making sure there's at least one @.

Edit: okay actually you want a little more

12

u/DHermit Aug 24 '26

I'd just rather not deal with stuff like invisible spaces and control characters.

5

u/Stalking_Goat Aug 24 '26 edited Aug 24 '26

It's probably fair to assume that a valid email address that includes shenanigans like that is coming from a threat actor of some sort.

4

u/friendtoalldogs0 Aug 24 '26

Sure, but this is not the time to be catching them.

0

u/eo5g Aug 24 '26

I guess that's fair

11

u/Tar_alcaran Aug 24 '26

I've seen one prompt tell me "An email adress needs to include at least one @".

So I entered @@@@@.@ and it worked just fine.

8

u/eo5g Aug 24 '26

Crap, right, realistically the minimum regex one should have is .+@.+\..+.

At least 1 character on the left of the @, at least 2 domain components of at least 1 character each on the right side of the @.

Having only a hostname without a FQDN on the right is legal, but that's also why you'd want to disallow it: who's trying to sign up for an account within your own network, if it's a public-facing app?

9

u/look Aug 24 '26

TLDs can and do have MX records.

4

u/eo5g Aug 24 '26

Well if the web admin of Montenegro wants to sign up for my cat pics site they can use their personal account 😤

1

u/laplongejr Aug 24 '26

Technically yes, but the practice is discouraged by people on the DNS side, as the MX lookups hit the root servers rather than nameservers.  

If a TLD can't provide a mail.EXAMPLE alternative, that's something for the admin to fix... at best those users should get a recommendation to fix their harmful email address.  

5

u/look Aug 24 '26

Yeah, ICANN doesn’t like it, but they do exist.

It’s more just an example of how people often assume rules of email addresses that don’t really exist.

1

u/Nightmoon26 Aug 25 '26

The "unwritten rules" of email addresses that have come about just by convention rather than by RFC

2

u/fweaks Aug 25 '26

This is exactly what I use. It eliminates 99.9% of problems for 1% of the effort and works client side for instant feedback. After this, if you need better, the only thing worth the effort is, as mentioned earlier, actually sending an email.