# Email Address

Key: `identity.person.email`

Standard email address (RFC 5322 simplified). Format: local@domain. Universal format but may include internationalized domain names (IDN).

Page: <https://meridian.online/docs/projects/finetype/types/identity/person/email>

Samples: `john.smith@example.com`, `user+tag@domain.org`, `test123@company.co.uk`

## Background

### Origin

RFC 5322, Internet Message Format, published in October 2008, defines the syntax of an address specification, or addr-spec.[[1]](https://www.rfc-editor.org/rfc/rfc5322) RFC 5322 obsoletes RFC 2822.[[1]](https://www.rfc-editor.org/rfc/rfc5322) RFC 5322 describes an addr-spec as a locally interpreted string followed by the at-sign character, followed by an Internet domain.[[1]](https://www.rfc-editor.org/rfc/rfc5322) The local-part may be written as a dot-atom or as a quoted-string, and the dot-atom form should be used whenever the string can be represented that way.[[1]](https://www.rfc-editor.org/rfc/rfc5322)

RFC 5321, the Simple Mail Transfer Protocol, sets the maximum length of a local-part at 64 octets.[[2]](https://www.rfc-editor.org/rfc/rfc5321) RFC 5321 sets the maximum length of a domain name at 255 octets.[[2]](https://www.rfc-editor.org/rfc/rfc5321) A verified erratum to RFC 3696 says the upper limit on address lengths should normally be considered to be 254.[[3]](https://errata.rfc-editor.org/eid1690) The erratum explains that the 256-octet path limit includes the angle brackets, which leaves 254 characters for the address itself.[[3]](https://errata.rfc-editor.org/eid1690)

RFC 6531, published in February 2012, specifies an SMTP extension for transport and delivery of email messages with internationalized email addresses.[[4]](https://www.rfc-editor.org/rfc/rfc6531) The extension is announced with the EHLO keyword SMTPUTF8.[[4]](https://www.rfc-editor.org/rfc/rfc6531) RFC 6532 allows use of Unicode in mail addresses and most header field content.[[5]](https://www.rfc-editor.org/rfc/rfc6532)

### Use

The HTML Standard defines its own valid email address syntax for form inputs.[[6]](https://html.spec.whatwg.org/multipage/input.html) The HTML Standard calls that definition a willful violation of RFC 5322.[[6]](https://html.spec.whatwg.org/multipage/input.html) Its stated reason is that the RFC 5322 syntax is too strict before the @, too vague after it, and too lax in allowing comments, whitespace and quoted strings.[[6]](https://html.spec.whatwg.org/multipage/input.html)

Many organisations treat uppercase and lowercase letters in the local-part as equivalent.[[7]](https://en.wikipedia.org/wiki/Email_address)

Subaddressing, also known as plus addressing, tagged addressing or mail extensions, treats an address as an alias to a prefix of its local-part.[[7]](https://en.wikipedia.org/wiki/Email_address) Gmail says that emails sent to any dotted version of a Gmail address will only go to the same account holder.[[8]](https://support.google.com/mail/answer/7436150?hl=en) Gmail notes that for work, school or other organisation accounts, dots do change the address.[[8]](https://support.google.com/mail/answer/7436150?hl=en) When you count unique people from an email column, decide up front whether tags after a plus sign and dots in Gmail local-parts should be folded together, and record that choice, because it changes the answer. (Meridian's view)

The Frictionless Table Schema specification gives string fields an email format, defined as a valid email address.[[9]](https://datapackage.org/standard/table-schema/)

## Sources

1. [RFC 5322: Internet Message Format](https://www.rfc-editor.org/rfc/rfc5322) — standard
2. [RFC 5321: Simple Mail Transfer Protocol](https://www.rfc-editor.org/rfc/rfc5321) — standard
3. [Erratum 1690 - RFC 3696](https://errata.rfc-editor.org/eid1690) — standard
4. [RFC 6531: SMTP Extension for Internationalized Email](https://www.rfc-editor.org/rfc/rfc6531) — standard
5. [RFC 6532: Internationalized Email Headers](https://www.rfc-editor.org/rfc/rfc6532) — standard
6. [HTML Standard](https://html.spec.whatwg.org/multipage/input.html) — standard
7. [Email address - Wikipedia](https://en.wikipedia.org/wiki/Email_address) — secondary source
8. [Dots don't matter in Gmail addresses - Gmail Help](https://support.google.com/mail/answer/7436150?hl=en) — documentation
9. [Table Schema \| Data Package Standard](https://datapackage.org/standard/table-schema/) — documentation