From b7c15c31519dc44c1f691e0466badd556ffe9423 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 18:18:56 +0200 Subject: Adding upstream version 3.7.10. Signed-off-by: Daniel Baumann --- proto/SMTPUTF8_README.html | 399 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 399 insertions(+) create mode 100644 proto/SMTPUTF8_README.html (limited to 'proto/SMTPUTF8_README.html') diff --git a/proto/SMTPUTF8_README.html b/proto/SMTPUTF8_README.html new file mode 100644 index 0000000..c0e5608 --- /dev/null +++ b/proto/SMTPUTF8_README.html @@ -0,0 +1,399 @@ + + + + + + +Postfix SMTPUTF8 support + + + + + + + +

+Postfix SMTPUTF8 support +

+ +

Overview

+ +

This document describes Postfix support for Email Address +Internationalization (EAI) as defined in RFC 6531 (SMTPUTF8 extension), +RFC 6532 (Internationalized email headers) and RFC 6533 (Internationalized +delivery status notifications). Introduced with Postfix version +3.0, this fully supports UTF-8 email addresses and UTF-8 message +header values.

+ +

Topics covered in this document:

+ +

Building with/without SMTPUTF8 support + +
Enabling Postfix SMTPUTF8 support + +
Using Postfix SMTPUTF8 support + +
SMTPUTF8 autodetection + +
Limitations of the current implementation + +
Compatibility with pre-SMTPUTF8 environments + +
Compatibility with IDNA2003 + +
Credits + +

+ +

Building Postfix with/without SMTPUTF8 support

+ +

Postfix will build with SMTPUTF8 support if the ICU version +≥ 46 library and header files are installed on the system. The +package name varies with the OS distribution. The table shows package +names for a number of platforms at the time this text was written. +

+ +

+ + + + + + + + + + + +
OS Distribution Package
FreeBSD, NetBSD, etc. icu
Centos, Fedora, RHEL libicu-devel
Debian, Ubuntu libicu-dev
+ +

OS Distribution	Package
FreeBSD, NetBSD, etc.	icu
Centos, Fedora, RHEL	libicu-devel
Debian, Ubuntu	libicu-dev

+ +

To force Postfix to build without SMTPUTF8, specify:

+ +

+$ make makefiles CCARGS="-DNO_EAI ..."
+

+ +

See the INSTALL document for more "make makefiles" options.

+ +

Enabling Postfix SMTPUTF8 support

+ +

There is more to SMTPUTF8 than just Postfix itself. The rest +of your email infrastructure also needs to be able to handle UTF-8 +email addresses and message header values. This includes SMTPUTF8 +protocol support in SMTP-based content filters (Amavisd), LMTP +servers (Dovecot), and down-stream SMTP servers.

+ +

Postfix SMTPUTF8 support is enabled by default, but it may be +disabled as part of a backwards-compatibility safety net (see the +COMPATIBILITY_README file).

+ +

SMTPUTF8 support is enabled by setting the smtputf8_enable +parameter in main.cf:

+ +

+# postconf "smtputf8_enable = yes"
+# postfix reload
+

+ +

(With Postfix ≤ 3.1, you may also need to specify "option_group += client" in Postfix MySQL client files, to enable UTF8 support +in MySQL queries. This setting is the default as of Postfix 3.2.)

+ +

With SMTPUTF8 support enabled, Postfix changes behavior with +respect to earlier Postfix releases:

+ +

UTF-8 is permitted in the myorigin parameter value. However, +the myhostname and mydomain parameters must currently specify +ASCII-only domain names. This limitation may be removed later.
+ +
UTF-8 is the only form of non-ASCII text that Postfix +supports in access tables, address rewriting tables, and other +tables that are indexed with an email address, hostname, or domain +name.
+ +
The header_checks-like and body_checks-like features are +not UTF-8 enabled, and therefore they do not enforce UTF-8 syntax +rules on inputs and outputs. The reason is that non-ASCII text may +be sent in encodings other than UTF-8, and that real email sometimes +contains malformed headers. Instead of skipping non-UTF-8 content, +Postfix should be able to filter it. You may try to enable UTF-8 +processing by starting a PCRE pattern with the sequence (*UTF8), +but this is will result in "message not accepted, try again later" +errors when the PCRE pattern matcher encounters non-UTF-8 input. +Other features that are not UTF-8 enabled are smtpd_command_filter, +smtp_reply_filter, the *_delivery_status_filter features, and the +*_dns_reply_filter features (the latter because DNS is by definition +an ASCII protocol).
+ +

The Postfix SMTP server announces SMTPUTF8 support in the +EHLO response.

+ +

+220 server.example.com ESMTP Postfix
+EHLO client.example.com
+250-server.example.com
+250-PIPELINING
+250-SIZE 10240000
+250-VRFY
+250-ETRN
+250-STARTTLS
+250-AUTH PLAIN LOGIN
+250-ENHANCEDSTATUSCODES
+250-8BITMIME
+250-DSN
+250 SMTPUTF8
+

+ +

The Postfix SMTP server accepts the SMTPUTF8 request in +MAIL FROM and VRFY commands.
+ +
```
+MAIL FROM:<address> SMTPUTF8 ...
+
+VRFY address SMTPUTF8
+
```
+ +
The Postfix SMTP client may issue the SMTPUTF8 request in +MAIL FROM commands.
+ +
The Postfix SMTP server accepts UTF-8 in email address +domains, but only after the remote SMTP client issues the +SMTPUTF8 request in MAIL FROM or VRFY commands.
+ +

+ +

Postfix already permitted UTF-8 in message header values +and in address localparts. This does not change.

+ +

Using Postfix SMTPUTF8 support

+ +

After Postfix SMTPUTF8 support is turned on, Postfix behavior +will depend on 1) whether a remote SMTP client requests SMTPUTF8 +support, 2) the presence of UTF-8 content in the message envelope +and headers, and 3) whether a down-stream SMTP (or LMTP) server +announces SMTPUTF8 support.

+ +

When the Postfix SMTP server receives a message WITHOUT +the SMTPUTF8 request, Postfix handles the message as it has always +done (at least that is the default, see autodetection below). +Specifically, the Postfix SMTP server does not accept UTF-8 in the +envelope sender domain name or envelope recipient domain name, and +the Postfix SMTP client does not issue the SMTPUTF8 request when +delivering that message to an SMTP or LMTP server that announces +SMTPUTF8 support (again, that is the default). Postfix will accept +UTF-8 in message header values and in the localpart of envelope +sender and recipient addresses, because it has always done that. +
+ +
When the Postfix SMTP server receives a message WITH the +SMTPUTF8 request, Postfix will issue the SMTPUTF8 request when +delivering that message to an SMTP or LMTP server that announces +SMTPUTF8 support. This is not configurable.
+ +
When a message is received with the SMTPUTF8 request, +Postfix will deliver the message to a non-SMTPUTF8 SMTP or LMTP +server ONLY if:
+ +
- No message header value contains UTF-8.
  + +
- The envelope sender address contains no UTF-8,
  + +
- No envelope recipient address for that specific + SMTP/LMTP delivery transaction contains UTF-8.
  + +
  
  NOTE: Recipients in other email delivery + transactions for that same message may still contain UTF-8. +
  
  + +
+ +
Otherwise, Postfix will return the recipient(s) for that + email delivery transaction as undeliverable. The delivery status + notification message will be an SMTPUTF8 message. It will therefore + be subject to the same restrictions as email that is received + with the SMTPUTF8 request.
+ +
When the Postfix SMTP server receives a message with the +SMTPUTF8 request, that request also applies after the message is +forwarded via a virtual or local alias, or $HOME/.forward file. +
+ +

+ +

SMTPUTF8 autodetection

+ +

This section applies only to systems that have SMTPUTF8 support +turned on (smtputf8_enable = yes).

+ +

For compatibility with pre-SMTPUTF8 environments, Postfix does +not automatically set the "SMTPUTF8 requested" flag on messages +from non-SMTPUTF8 clients that contain a UTF-8 header value or +UTF-8 address localpart. This would make such messages undeliverable +to non-SMTPUTF8 servers, and could be a barrier to SMTPUTF8 adoption. +

+ +

By default, Postfix sets the "SMTPUTF8 requested" flag only on +address verification probes and on Postfix sendmail submissions +that contain UTF-8 in the sender address, UTF-8 in a recipient +address, or UTF-8 in a message header value.

+ +

+/etc/postfix/main.cf:
+    smtputf8_autodetect_classes = sendmail, verify
+

+ +

However, if you have a non-ASCII myorigin or mydomain setting, +or if you have a configuration that introduces UTF-8 addresses with +virtual aliases, canonical mappings, or BCC mappings, then you may +have to apply SMTPUTF8 autodetection to all email:

+ +

+/etc/postfix/main.cf:
+    smtputf8_autodetect_classes = all
+

+ +

This will, of course, also flag email that was received without +SMTPUTF8 request, but that contains UTF-8 in a sender address +localpart, receiver address localpart, or message header value. +Such email was not standards-compliant, but Postfix would have +delivered it if SMTPUTF8 support was disabled.

+ +

Limitations of the current implementation +

+ +

The Postfix implementation is a work in progress; limitations +are steadily being removed. The text below describes the situation +at one point in time.

+ +

No automatic conversions between ASCII and UTF-8 domain names.

+ +

Some background: According to RFC 6530 and related documents, +an internationalized domain name can appear in two forms: the UTF-8 +form, and the ASCII (xn--mumble) form. An internationalized address +localpart must be encoded in UTF-8; the RFCs do not define an ASCII +alternative form.

+ +

Postfix currently does not convert internationalized domain +names from UTF-8 into ASCII (or from ASCII into UTF-8) before using +domain names in SMTP commands and responses, before looking up +domain names in lists such as mydestination, relay_domains or in +lookup tables such as access tables, etc., before using domain names +in a policy daemon or Milter request, or before logging events. +

+ +

Postfix does, however, casefold domain names and email addresses +before matching them against a Postfix configuration parameter or +lookup table.

+ +

In order to use Postfix SMTPUTF8 support:

+ +

The Postfix parameters myhostname and mydomain must be in +ASCII form. One is a substring of the other, and the myhostname +value is used in SMTP commands and responses that require ASCII. +The parameter myorigin (added to local addresses without domain) +supports UTF-8.
+ +
You need to configure both the ASCII and UTF-8 forms of +an Internationalized domain name in Postfix parameters such as +mydestination and relay_domains, as well as lookup table search +keys.
+ +
Milters, content filters, policy servers and logfile +analysis tools need to be able to handle both the ASCII and UTF-8 +forms of Internationalized domain names.
+ +

+ +

Compatibility with pre-SMTPUTF8 +environments

+ +

Mailing lists with UTF-8 and non-UTF-8 subscribers

+ +

With Postfix, there is no need to split mailing lists into UTF-8 and +non-UTF-8 members. Postfix will try to deliver the non-UTF8 subscribers +over "traditional" non-SMTPUTF8 sessions, as long as the message +has an ASCII envelope sender address and all-ASCII header values. +The mailing list manager may have to apply RFC 2047 encoding to +satisfy that last condition.

+ +

Pre-existing non-ASCII email flows

+ +

With "smtputf8_enable = no", Postfix handles email with non-ASCII +in address localparts (and in headers) as before. The vast majority +of email software is perfectly capable of handling such email, even +if pre-SMTPUTF8 standards do not support such practice.

+ +

Rejecting non-UTF8 addresses

+ +

With "smtputf8_enable = yes", Postfix +requires that non-ASCII address information is encoded in UTF-8 and +will reject other encodings such as ISO-8859. It is not practical +for Postfix to support multiple encodings at the same time. There +is no problem with RFC 2047 encodings such as "=?ISO-8859-1?Q?text?=", +because those use only characters from the ASCII characterset.

+ +

Rejecting non-ASCII addresses in non-SMTPUTF8 transactions

+ +

Setting "strict_smtputf8 = yes" in addition to "smtputf8_enable += yes" will enable stricter enforcement of the SMTPUTF8 protocol. +Specifically, the Postfix SMTP server will not only reject non-UTF8 +sender or recipient addresses, it will in addition accept UTF-8 +sender or recipient addresses only when the client requests an +SMTPUTF8 mail transaction.

+ +

Compatibility with IDNA2003

+ +

Postfix ≥ 3.2 by default disables the 'transitional' +compatibility between IDNA2003 and IDNA2008, when converting UTF-8 +domain names to/from the ASCII form that is used in DNS lookups. +This makes Postfix behavior consistent with current versions of the +Firefox and Chrome web browsers. Specify "enable_idna2003_compatibility += yes" to get the historical behavior.

+ +

This affects the conversion of domain names that contain for +example the German sz (ß) and the Greek zeta (ς). See +http://unicode.org/cldr/utility/idna.jsp for more examples.

+ +

Credits

+ +

May 15, 2014: Arnt Gulbrandsen posted his patch for Unicode +email support. This work was sponsored by CNNIC.
+ +
July 15, 2014: Wietse integrated Arnt Gulbrandsen's code +and released Postfix with SMTPUTF8 support.
+ +
January 2015: Wietse added UTF-8 support for casefolding +in Postfix lookup tables and caseless string comparison in Postfix +list-based features.
+ +

+ + + + + -- cgit v1.2.3