Check one address or a whole list for syntax errors, mistyped providers, disposable domains and role accounts. Nothing is uploaded or looked up.
Two different questions hide inside “is this email valid?”. One is settled: whether the address is shaped the way the standards say an address must be shaped. The other, whether anyone reads mail sent to it, needs a DNS lookup and a conversation with a mail server, and no page in a browser can have that conversation. Email Address Validator answers the first question properly and is explicit about not answering the second.
That split runs through the whole output. A hard error means the address cannot be valid under RFC 5322 and no mail server will take it. A warning means the address is well-formed but probably not what someone meant to type. Conflating those two is how validators end up rejecting on-call+payments@harbourline.dev, which is perfectly legal, while waving through priya@gmial.com.
Press Load Sample for a signup list of seven. Two are rejected outright: r.okonkwo@@northwind-labs.io has a second @ where the name should be, and .leading.dot@quartzandkiln.co.uk returns “The part before the @ cannot start with a dot.” Three of the five that pass still carry a warning: priya.raghunathan@gmial.com is offered gmail.com with a Fix button that rewrites the line in place, billing@… is flagged as a role address rather than a person, and temp-signup@mailinator.com is named as disposable. The remaining two are simply fine and say nothing at all, which is the point of grading rather than scoring.
!#$%&'*+/=?^_`{|}~-, which RFC 5322 lists as ordinary name characters. A validator that rejects them is rejecting real mailboxes."odd name"@example.com is valid, and the space check has to run after the address is split rather than before, or that address is wrongly rejected. It earns a warning anyway, because plenty of systems will not take it.admin@192.0.2.55 is rejected with the fix in the message: written as admin@[192.0.2.55] it becomes a legal address literal, and the tool then warns that it is only useful inside a network you control.Nothing here contacts a mail server, checks an MX record, or asks a provider whether a mailbox exists, so a green tick means the address is spelled correctly and nothing more. The disposable-domain list holds 16 well-known providers and will always trail the ones invented last month. Where the tool does earn its keep on a list is the pass at the end: Copy valid only gives back the addresses that survived, already cleaned of the broken lines, and the filters above the results let you look at just the failures or just the ones worth a second glance. Batches stop at 200 addresses, and everything stays in this tab, which matters when the list is your customers.