Once upon a time in the past ...

Posted Dec 5, 2024 19:11 UTC (Thu) by rweikusat2 (subscriber, #117920)
Parent article: Debian opens a can of username worms

… people used a weird text messaging system called email to send, well, text messages to users supposed to be delivered into their mailboxes at certain hosts. The email address of a user user on host host would be user@host. IOW, a unix username is also what RFC5322 calls the local-part of an email address. And this means ASCII, even according to the newest specification.

https://datatracker.ietf.org/doc/html/rfc5322

Once upon a time in the past ...

Posted Dec 5, 2024 20:25 UTC (Thu) by storner (subscriber, #119) [Link] (2 responses)

I think you are mistaken about requiring ASCII for the name of the mailbox. The RFC you refer to says (section 3.4.1):

The local-part portion is a domain-dependent string. In addresses,
it is simply interpreted on the particular host as a name of a
particular mailbox.

"Domain-dependent" means that there are really no rules as to which characters can be used. It can even be quoted to allow whitespace.

Once upon a time in the past ...

Posted Dec 5, 2024 21:02 UTC (Thu) by rweikusat2 (subscriber, #117920) [Link] (1 responses)

The grammar rule defining local-part,

local-part = dot-atom / quoted-string / obs-local-part

is at the beginning of the RFC page which contains the statement

The local-part portion is a domain-dependent string.

The claim that domain-dependent would mean "no requirements" is thus obviously wrong. dot-atom and quoted-string are defined in sections 3.2.3 ("Atom") and 3.2.4 ("Quoted Strings"). Drilling down to the actual character set specifications always ends with a subset of ASCII, the most liberal one being the one for quoted strings which includes whitespace and all printable characters, ie, codepoints 32 - 126.

Once upon a time in the past ...

Posted Dec 5, 2024 21:04 UTC (Thu) by rweikusat2 (subscriber, #117920) [Link]

Slight correction: The quoted-string character set excludes \ and ".

Once upon a time in the past ...

Posted Dec 6, 2024 4:38 UTC (Fri) by jheiss (subscriber, #62556) [Link] (10 responses)

RFC 6532 extends 5322 to allow UTF-8 in email addresses in message headers, and 6531 extends 5321 (SMTP) to allow UTF-8 in SMTP addressing. There are some draft documents in the IETF mailmaint working group which try to set some guidelines about mixed languages and other possibly confusing situations, but servers that implement 6531/6532 could allow any combination of UTF-8 characters in usernames.

Once upon a time in the past ...

Posted Dec 9, 2024 13:24 UTC (Mon) by zdzichu (subscriber, #17118) [Link] (9 responses)

Just tried it. I've put 😒 (unamused face) into /etc/aliases for consumption by my Postfix. Then I've sent an email from Gmail to 😒@pipebreaker.pl. It came through!

I'll remove this alias next week. Until them you can email me at above address to check your email setup ;)

Once upon a time in the past ...

Posted Dec 9, 2024 14:42 UTC (Mon) by geert (subscriber, #98403) [Link]

git send-email doesn't like it:

| error: unable to extract a valid address from: 😒@pipebreaker.pl
| What to do with this address? ([q]uit|[d]rop|[e]dit):

Where's the "[f]orce" option? ;-)

Once upon a time in the past ...

Posted Dec 9, 2024 15:51 UTC (Mon) by dskoll (subscriber, #1630) [Link]

The Postfix server on my LAN had no problems with 😒@... but my Sendmail relay host rejected it.

<😒@pipebreaker.pl>: host 192.168.xx.yy[192.168.xx.yy] said: 501 5.1.3 8-bit
    character in mailbox address "<p???@pipebreaker.pl>" (in reply to RCPT TO
    command)

Once upon a time in the past ...

Posted Dec 9, 2024 17:21 UTC (Mon) by raven667 (subscriber, #5198) [Link] (2 responses)

Fun, I tried thunderbird through o365 and Gmail, we'll see how it goes. The Gmail phone app rejected the address with an error popup as did the outlook phone app by marking it red and silently disabling the send button. No bounces yet.

Once upon a time in the past ...

Posted Dec 9, 2024 18:24 UTC (Mon) by zdzichu (subscriber, #17118) [Link] (1 responses)

Got one from you, replied.

I also got one from Alejandro, but did not manage to reply with fancy From:

SMTPUTF8 is required, but was not offered by host smtp3.kernel.org[44.230.10.245]

Once upon a time in the past ...

Posted Dec 9, 2024 20:05 UTC (Mon) by raven667 (subscriber, #5198) [Link]

My attempt through O365 was thwarted because our ProofPoint anti-malware/phishing system doesn't support utf8 addresses, but the `550 5.1.17 SMTPSEND.Utf8RecipientAddress; UTF-8 recipient address not supported.` bounce was filtered into Junk, lol.

The reply to Gmail with an ASCII address worked but the utf8 From reply was also filtered into Junk, but it did work.

I'm guessing that fake bounce messages are more commonly used for spam/phishing than real notifications which is why they are Junked repeatedly on totally different systems.

Once upon a time in the past ...

Posted Dec 9, 2024 18:24 UTC (Mon) by wtarreau (subscriber, #51152) [Link]

I don't even have that key on my keyboard. Good luck to those trying to do funny things with UTF-8, often the first problem is to permit others to type them. That's by far the least inclusive thing that was ever invented in the computer world :-/

GNUS

Posted Dec 10, 2024 8:18 UTC (Tue) by SiB (subscriber, #4048) [Link] (1 responses)

Emacs GNUS:
Address ‘😒@pipebreaker.pl’ (=?utf-8?Q?=F0=9F=98=92?=@pipebreaker.pl) might be bogus. Continue? (y or n) y
Sending...
Sending via mail...
message-send-mail-with-sendmail: Sending...failed to 2024-12-10 09:17:47 1tKvRD-000000003Sv-2FNl bad addresses found in headers;

Exim4

Posted Dec 10, 2024 8:27 UTC (Tue) by SiB (subscriber, #4048) [Link]

Correction: The error message came fom exim4:

=?utf-8?Q?=3C=F0=9F=98=92?=@pipebreaker.pl>: malformed address: >
may not follow =?utf-8?Q?=3C=F0=9F=98=92?=@pipebreaker.pl

Somehow, gnus was confused by the <> around the address. Without <>, exim4 did a graylisted delivery attempt.

Once upon a time in the past ...

Posted Dec 10, 2024 11:29 UTC (Tue) by farnz (subscriber, #17727) [Link]

I've tried this with Exim and KMail; I can send just fine, but because I've not turned on Exim SMTPUTF8 support (in part because I need to test what Cyrus IMAPd thinks of UTF-8 in local parts), no reply comes through.