4 ms·

Most internet systems can also assume there will be at least one dot following the @ symbol and at least two characters after that. Something intended for us o

• jeroenhd 5y ago
  The two character requirements can trip up foreign TLDs if the input is encoded as unicode (but everyone knows you're supposed to translate the domain to IDN before running validation, right? Right??) so I wouldn't even use that. There don't seem to be any TLDs that are only one character long in their encoded form, but I can easily see Chinese or Japanese TLDs leveraging their extensive character set to keep the TLD part of the domain short. As long as there's something behind the @ before a period, it's probably fine for an external email address. Missing a period can cause problems, because without a period or a TLD at the end, your mail service might try to send email to internal servers in your network. Send mail to a@b from server c.com and you might end up sending email to a@b.c.com instead. Not checking for a period in the domain part can therefore cause some pretty weird behaviour. If the email ends in an external domain, there's a period. If the email is intended for an internal host without a full domain name, the period should be at the very end of the address, turning it into a proper hostname. It's easy for people to type gmailcom and if you're using dot less domains in your network infrastructure you probably know about these hacks anyway. I don't think checking for a dot will break anything, even in the spec, except for something@[IPv6 address] but IP address emails are practically unused in real life anyway.