Talk:Email address

Recent reversion by 80.108.8.19

IP address 80.108.8.19 recently reverted a change by user:Snori, with the description "Fully qualified domains end with a dot. Reverting the comment-less vandalism". While I would have preferred that user:Snori provide a comment, his removal of the trailing dot from the FQDN was correct: unlike the syntax of RFC 1034 and RFC 1035, there is no trailing period in the RFC 5321 domain name. Shmuel (Seymour J.) Metz Username:Chatul (talk) 23:41, 2 November 2017 (UTC)

Prevalence of tagged addresses?

Some e-mail servers ignore everything after a plus sign (less commonly, a minus sign) so that the user can hand out different addresses to different organizations and thus know who has sold his address without authorization. Email address#Local-part claims "Note that characters after a plus sign + are generally ignored", which seems too strong. Certainly there are servers that do so, and they may even be common, but they are not the norm. Shmuel (Seymour J.) Metz Username:Chatul (talk) 17:00, 18 January 2018 (UTC)

Quoted space as the full local part?

Currently, the quoted space as the full local part (" "@example.com, or even \ @example.com) is listed as invalid. Does someone know why, since the RFC allows quoted spaces and doesn't say anything about the local part having at least one non-space character? -- Poromenos (talk) 03:48, 11 February 2018 (UTC)

Style for listing IETF RFC and STD docuuments

Would it be desirable to update the references to use {{IETF RFC}}, {{cite IETF|rfc=}} and {{cite IETF|std=}} instead of plain text and <NOWIKI>text</NOWIKI> blocks? Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:58, 15 January 2019 (UTC)

• Yes. Even if it isn't today, it could become so in the future. Andy Dingley (talk) 21:20, 15 January 2019 (UTC)

  Should every mention of an RFC use {{IETF RFC}} or only the first in each section? --Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:50, 22 January 2023 (UTC)

No addresses commonly used?

Quoting article:

"This article uses the term email address to refer to the addr-spec defined in RFC 5322, not to the address that is commonly used; the difference is that an address may contain a display name, a comment, or both."

That seems silly in an artcle about email. Why not addresses commonly used? That's what I'm trying to recreate from 3-year-old memories. Just a short section with some typical examples would do. Was it:
(Joe Blow) jblow@acme.com ?
(The "+" section seemed close, but no cigar.)

Also one place jargon should be STRICTLY FORBIDDEN is the table of contents, of which is about half. This article seems designed strictly for sysadmins, etc. Like: display name ?
— Preceding unsigned comment added by 2602:306:CFCE:1EE0:3044:A2C3:2683:987B (talk) 19:35, 5 April 2019 (UTC)

When the nomenclature in an article on a technical subject differs from that in the literature, then the text should make that clear. The usage of "address" in the article matches the definition of "mailbox" in RFC 5321, not the definition of "address" in RFC 5322.

Per the definitions in RFC5321 and FC5322, "Foo Bar <foo@bar.com>" is an address; "<foo@bar.com" is both an address and a mailbox. Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:17, 21 August 2019 (UTC)

References

Edit by 117.237.210.103

Could the edit by 117.237.210.103 be referring to source routing as one of the three parts of an address? Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:40, 11 October 2019 (UTC)

@Chatul: I think you mean the edits by PremKwiki (talk · contribs); the IP just undid one of the edits and I undid the other one. The text at the URL in their edit summary listed the "@" character as the second part. I wouldn't call it incorrect, but I think the original text of the article better matches the common usage of the term "part" and as a result is more understandable. –LiberatorG (talk) 21:06, 11 October 2019 (UTC)

Please read the relevant RFCs before making changes based on what the editor presumes is in them

The article has links to, e.g., RFC 5321, RFC 5322; it's not that difficult to read them instead of making incorrect changes based on assumptions. Shmuel (Seymour J.) Metz Username:Chatul (talk) 01:53, 23 February 2020 (UTC)

'Dot-string'?

"A local part is either a Dot-string or a Quoted-string..." - have no idea what a dot string is. Guesses don't count.

Refactoring, or a 'Dot-string' link would be useful / appreciated. — Preceding unsigned comment added by Bs27975 (talk • contribs) 16:58, 23 July 2020 (UTC)

Those are definitions in RFC 5321. There are multiple citations of that document, with different sections, different quotations, or both, and I'd like to cut out the redundancy without losing information, but I'm not sure how best to retain the functionality of {{cite IETF}} while rendering the common information only once. Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:21, 23 July 2020 (UTC)

References

Status of RFC 5322

RFC 5322 is not outdated per the [IETF]; if a PHP validator fails on a quoted local part containing a space then the validator is broken. Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:38, 13 December 2020 (UTC)

One thing this article seems to be very strict on is, "this is what the RFCs say", but seem to lack practical warnings against doing what is "technically allowed". One can certainly set up a server and allow someone the mail address of "technically allowed"@example.com, but a huge number of users on the internet will simply not be able to send e-mail to that address (because it is a post year 2000 extension that many providers simply will not deal with). Today, one cannot sent such an outbound e-mail via Google's email services, for one example that I'm able to test right now. (( Even though the allowance is much newer, Internationalized (UTF8) local parts are much more accepted )). Vollink (talk) 19:30, 27 September 2022 (UTC)

I agree that adding a list of technically valid but problematic addresses would be useful, and that Despite the wide range of special characters which are technically valid, organisations, mail services, mail servers and mail clients in practice often do not accept all of them. For example, Windows Live Hotmail only allows creation of email addresses using alphanumerics, dot (.), underscore (_) and hyphen (-). Common advice is to avoid using some special characters to avoid the risk of rejected emails. could well be expanded}} --Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:34, 28 September 2022 (UTC)

References

include examples with subdomains?

As far as I understand the introduction "With the introduction of internationalized domain names, efforts are progressing to permit non-ASCII characters in email addresses." it also means that anything after the @ is either different from a valid domain name or at least only a true subset. Yet all examples only differs in anything before the "@" - and the comment in brackets. Would it be useful to just inline "john.doe@sub.example.com"? --2001:A62:1963:BA01:B880:2BA:CCE8:633D (talk) 14:18, 22 July 2021 (UTC)

No, it means that some addresses are now allowed with SMTPUTF8 that are invalid without it; it doesn't mean that every domain must have non-ASCII characters. The first example in Email address#Internationalization examples has a domain that is pure ASCII.

The examples in Email address#Local-part all have the same domain. The addresses in In contrast to unquoted local-parts, the addresses ".John.Doe"@example.com, "John.Doe."@example.com and "John..Doe"@example.com are allowed. are individually in <code>...</code> pairs; I don't understand what you mean by inlining them.

As for "john.doe@sub.example.com", john.doe@sub.example.com has an unquoted local part and doesn't belong in that sentence. If you want an example of a three level domain, the place to put it is Email address#Examples. --Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:17, 22 July 2021 (UTC)

Incorrect part: no underscores in domain name

The example of a "bad email address" show this example: i_like_underscore@but_its_not_allowed_in_this_part.example.com. That doesn't seem to be correct as per RFC 2181, section 11, "Name syntax", as stated here. Also see rfc3696, sub 2: "Any characters, or combination of bits (as octets), are permitted in DNS [=domain] names." It continues: "However, there is a preferred form [...] the "LDH rule", [that] provides that the labels (words or strings separated by periods) that make up a domain name must consist of only the ASCII [ASCII] alphabetic and numeric characters, plus the hyphen." So, while preferred, it's not required. JHBonarius (talk) 08:29, 19 August 2021 (UTC)

In every way I read RFC 2181, section 11 (the section above quoted ), is specific to non-hostname resource records and those, in turn MIGHT include labels from hostname record types. That is, it's fine to have a weird binary string as a non-hostname resource record's label, but that doesn't automatically apply to MX, CNAME, A, or AAAA DNS records. But absolutely are used for things like TXT records (which are not expected to point to a hostname). That is, pay close attention to the first paragraph of that section. Vollink (talk) 19:09, 27 September 2022 (UTC)

Address literal instead of Internet domain name

I was reading the actual RFC for email and noticed it stopped mentioning allowing numerical values starting with RFC 2822. Prior RFCs (like RFC 822) had this language in their address specification section:

Note:  THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED.  It
    is  permitted  only  as  a means of bypassing temporary
    system limitations, such as name tables which  are  not
    complete.

This language is present in earlier RFCs, but this language disappears in 2822, and is also not present in 5322. There is a section in the addr-spec in 5322 that says:

 Note: A liberal syntax for the domain portion of addr-spec is
 given here.  However, the domain portion contains addressing
 information specified by and used in other protocols (e.g.,
 [RFC1034], [/rfc/rfc1035 RFC1035], [RFC1123],   [RFC5321]).  It is therefore
 incumbent upon implementations to conform to the syntax of
 addresses for the context in which they are used.

The RFC for the SMTP protocol, RFC5321 does have a section about using address literals in the domain portion Address Literals.

Some email clients will let you enter an address with address literals, but a lot do not. Some mail delivery subsystems will have problems with delivering mail in that format as well., particularly if there is mailbox ambiguity due to a mail server being responsible for multiple domains.

Generally to me, it seems that while SMTP does support address literals, it is not generally used or advised for actual user use for email addresses. My original intention on removing those sections were to steer people away from thinking this was a valid format, as it isn't given 5322. But it also IS valid for SMTP, and with the section about conforming to the syntax of the addresses for the context used, it's a little unclear how it should be handled. This page seems to be mostly focused on the addr-spec definition of an email address, which I think means it should mention how address literals are not really intended in that format since it does not appear in the addr-spec anymore. What do others think? Maybe I am missing something obvious? I am a novice at wiki so I figure the more experienced powerusers might have good input here. Martianant (talk) 00:17, 12 May 2023 (UTC)

One of the links that you provided, i.e., [/rfc/rfc1035 RFC1035] for RFC 5325, is malformed; I recommend that you change all of the RFC citations to either {{IETF RFC}} or {{cite ietf|rfc=}}

While some language deprecating it is gone, RFC 5322 still includes domain-literal and language describing the use of IP addresses. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 09:48, 12 May 2023 (UTC)

Even though SMTP is able to handle domain literals, such a use is not likely to work in most scenarios where DNS-based security mechanisms (such as SPF, DKIM and DMARC) have been implemented as recommended by relevant RFCs. In effect, SMTP will correctly handle a message with domain literals in the Sender or Envelope-sender header, but more often than not the message will be rejected by downstream MTAs. — kashmīrī ^TALK 11:04, 12 May 2023 (UTC)

There are two different IP questions that the article should discuss:

1. Is it valid to use an IP address as the domain part?
2. Is it prudent to have an IP address as the domain part?

IMHO, while the answer to the first is yes, the answer to the second is an empatic no; some e-mail operators regard a bare IP address as a red flag and will reject messages containing such mailbox references. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 11:25, 12 May 2023 (UTC)

I think it's valid and it's also valid for correctly configured MTAs not to deliver such messages. Such a small contradiction in the vast body of RFAs. — kashmīrī ^TALK 11:44, 12 May 2023 (UTC)

There is no contradiction; RFC 5321 is quite clear that "My server, my rules" applies to classifying attempted deliveries; look for "policy reasons". You are, of course, required to use the correct code to indicate rejection. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 17:52, 12 May 2023 (UTC)

References

Should cite RFC-5321 as relevant standard for address syntax, not RFC-5322

The syntax for header fields such as ‘From:’ and ‘To:’ include email addresses but also much more stuff. The syntax allowed for Mailbox addresses in SMTP is what most people think of as an “email address.”

Perhaps see [1] for suggested text to explain email address syntax, with citation of correct RFCs.

Does anyone think that an email address includes "group" syntax and "display-name" and the comments and folding white space of RFC 5322. doi:10.17487/RFC5322.? All that stuff can be part of the From: header value, but is not part of any address and is not used to deliver email.

If we can agree on the correct syntax to use, I can take a pass at this article to correct and simplify the text. Gene.hightower (talk) 22:16, 1 April 2024 (UTC)

Some definitions in RFC 5321 refer to definitions in RFC 5322.

I believe that most people think of an e-mail address as what appears in the From: header field; some (expletive deleted) software doesn't even show the mailbox.

However, the Transport section should definitely limit the term to mailbox, including group addresses. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:51, 2 April 2024 (UTC)

>> I believe that most people think of an e-mail address as what appears in the From: header field;

So when a web form asks for your email address, you put in “Seymour J Metz <…” starting with the ‘display-name’, then an angle bracket then the ‘addr-spec’? You do not. You put in something matching the ‘Mailbox’ rule from RFC-5322. As would 100 out of 100 people asked, is my guess.

>> some (explitive deleted) software doesn't even show the mailbox.

Some software shows only the ‘display-name’ in the From: header, that does *not* mean that ‘display-name’ is an email address. Or is even part of an email address. Gene.hightower (talk) 14:51, 3 April 2024 (UTC)

You do not. “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.”

Actually, I do often enter a display name. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:03, 3 April 2024 (UTC)

@Chatul Email address does not include the display name. Period. And I somehow don't believe that you enter your display name in, say, the Gmail login form[2] where it asks for "e-mail". — kashmīrī ^TALK 17:58, 3 April 2024 (UTC)

Why refute what I never wrote? Nothing in I do often enter a display name suggests that I enter it in a login field. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:26, 3 April 2024 (UTC)

RFC-5321 does not have any syntax for "group addresses" - not sure what you're talking about here. Gene.hightower (talk) 18:23, 3 April 2024 (UTC)

An RFC 5321 mailox can identify either an individual mailbox or a group. That's determined by the configuration of the MSA and there is no difference in the syntax. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:26, 3 April 2024 (UTC)

An email address can deliver to an individual or a group, but the syntax is the same. Gene.hightower (talk) 20:57, 3 April 2024 (UTC)

Are we accepting that 'Mailbox' from RFC-5321 should be understood as defining the syntax of an "email address" as discussed in this article?

I think it's fine to discuss message header fields (such as From: and To:) and how email addresses are used within them. Gene.hightower (talk) 21:07, 3 April 2024 (UTC)

>> Some definitions in RFC 5321 refer to definitions in RFC 5322.

They are companion documents, that should not confuse anybody. Gene.hightower (talk) 18:36, 3 April 2024 (UTC)

local-part length limit is incorrect

>> The maximum total length of the local-part of an email address is 64 octets.

Simply not true. Local parts much longer than this are commonly used and work fine with many email providers.

The applicable section of RFC-5321 is 4.5.3.1. ‘Size Limits and Minimums’ where is says: “To the maximum extent possible, implementation techniques that impose no limits on the length of these objects should be used.” Gene.hightower (talk) 00:22, 4 April 2024 (UTC)

Why did you drop the next sentence, "Objects larger than these sizes SHOULD be avoided when possible.", from that quote? That plus section 4.5.3.1.1. 'Local-part', which says "The maximum total length of a user name or other local-part is 64 octets.", ustifies the text in the article. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 13:03, 4 April 2024 (UTC)

I know that in practice ‘Local-part’s much larger than that are in common use, and work fine. The standard suggests that such long ‘Local-part’s SHOULD be avoided, but does not forbid their use. The statement in the artcle without more context provides no useful information, and seems misleading.

My quote did not “drop” anything. Curious readers should consult the original documents. Gene.hightower (talk) 17:35, 4 April 2024 (UTC)

Section on local-part syntax incorrect according to RFC-5321 OR RFC-5322.

>> Comments are allowed with parentheses at either end of the local-part

RFC-5322 allows comments, white space, and “folding” white space (CRLF followed by a space or tab) between any tokens, except “Comments and folding white space SHOULD NOT be used around the "@" in the addr-spec.”

RFC-5321 allows no comments at all. Gene.hightower (talk) 00:42, 4 April 2024 (UTC)

The text should make the context clear. In RFC 5321, Mailbox, used in Forward-path and Reverse-path, does not allow comments or white space anywhere.

In RFC 5322, mailbox allows CFWS only prior to the "<". A mailbox given as an addr-spec rather than as a name-addr may not contain CFWS.

Neither RFC defines email address or e-mail address.

Similarly, the text should reflect differences between RFC 6531 and RFC 6532, which obsolete RFC 5336 and RFC 5337. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 13:49, 4 April 2024 (UTC)

>> In RFC 5322, mailbox allows CFWS only prior to the "<"

In RFC-5322 an ‘addr-spec’ (which is what comes *after* the left angle

bracket in an ‘angle-addr’) starts with a ‘local-part’ which can be a

‘dot-atom’ which is an optional CFWS followed by a ‘dot-atom-text’

So, CFWS can appear on *both* sides of the "<". Gene.hightower (talk) 17:11, 4 April 2024 (UTC)

>> Neither RFC defines email address or e-mail address.

And this may be the root of the confusion for many people. The grammar

rule that maps to a conceptual “email address” is called ‘Mailbox’ in

RFC-5321, and is called ‘addr-spec’ in RFC-5322. Gene.hightower (talk) 17:16, 4 April 2024 (UTC)

You are correct about RFC 5322 dot-atom allowing CFWS, subject to the restriction in 3.4.1. 'Addr-Spec'. Specification.

No, the appropriate terms are Mailbox in RFC 5321 and mailbox in RFC 5321 (the terms differ in case.) Further, if you use the RFC 5321 definition, then all the text about comments is wrong. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 17:55, 4 April 2024 (UTC)

>> The text should make the context clear.

Except mixing syntax from both RFC-5321 and RFC-5322 when all we need to discuss the syntax of an “email address” is RFC-5321 causes very confused text throughout this article. Gene.hightower (talk) 17:18, 4 April 2024 (UTC)

I believe that there is a fundamental disagreement on what we need to address. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 17:55, 4 April 2024 (UTC)