Because I really don't want to accept a string with more (or less) than one @ symbol for an e-mail address. Such an address can be valid theoretically but chances are it is incorrect. If somebody submits such a string for their email, 99 in 100 cases it's a typo and the remaining 1 is a person testing you. Not even one real person in a million will use an e-mail address which doesn't have exactly one @ symbol in it.
People can also incorrectly type in their email in a way that looks fine, so I'm skeptical of intentionally not allowing valid email addresses just to cut out a small fraction of those. The isemail.info site recommends a warning if it doesn't look right, but allowing the user to override and use anyway, which seems sensible to me.
(I say this as the proud owner of a lastname.email domain, where the .email TLD was made explicitly for this 8 years, and I still have problems with bad validation.)
You can ask for confirmation if it’s an unusual construction, but denying it outright is user hostile.
Also, how many users are actually manually typing their e-mail address into a form, instead of using autofill?
As the referenced page says, a valid email address is one that can receive email. If you really care about the e-mail address being correct, then you need to validate it by sending a verification e-mail.
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Because I really don't want to accept a string with more (or less) than one @ symbol for an e-mail address. Such an address can be valid theoretically but chances are it is incorrect. If somebody submits such a string for their email, 99 in 100 cases it's a typo and the remaining 1 is a person testing you. Not even one real person in a million will use an e-mail address which doesn't have exactly one @ symbol in it.
People can also incorrectly type in their email in a way that looks fine, so I'm skeptical of intentionally not allowing valid email addresses just to cut out a small fraction of those. The isemail.info site recommends a warning if it doesn't look right, but allowing the user to override and use anyway, which seems sensible to me.
(I say this as the proud owner of a lastname.email domain, where the .email TLD was made explicitly for this 8 years, and I still have problems with bad validation.)
You can ask for confirmation if it’s an unusual construction, but denying it outright is user hostile.
Also, how many users are actually manually typing their e-mail address into a form, instead of using autofill?
As the referenced page says, a valid email address is one that can receive email. If you really care about the e-mail address being correct, then you need to validate it by sending a verification e-mail.
If somebody wants to register and use an email address with a bang path, that unix beard is out of luck.