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96 lines
3.8 KiB
Markdown
96 lines
3.8 KiB
Markdown
# Unicode support
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maddy has the first-class Unicode support in all components (modules). You do
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have to take any actions to make it work with internationalized domains,
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mailbox names or non-ASCII message headers.
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Internally, all text fields in maddy are represented in UTF-8 and handled using
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Unicode-aware operations for comparisons, case-folding and so on.
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## Non-ASCII data in message headers and bodies
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maddy SMTP implementation does not care about encodings used in MIME headers or
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in `Content-Type text/*` charset field.
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However, local IMAP storage implementation needs to perform certain operations
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on header contents. This is mostly about SEARCH functionality. For IMAP search
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to work correctly, the message body and headers should use one of the following
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encodings:
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- ASCII
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- UTF-8
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- ISO-8859-1, 2, 3, 4, 9, 10, 13, 14, 15 or 16
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- Windows-1250, 1251 or 1252 (aka Code Page 1250 and so on)
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- KOI8-R
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- ~~HZGB2312~~, GB18030
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- GBK (aka Code Page 936)
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- Shift JIS (aka Code Page 932 or Windows-31J)
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- Big-5 (aka Code Page 950)
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- EUC-JP
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- ISO-2022-JP
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_Support for HZGB2312 is currently disabled due to bugs with security
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implications._
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If mailbox includes a message with any encoding not listed here, it will not
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be returned in search results for any request.
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Behavior regarding handling of non-Unicode encodings is not considered stable
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and may change between versions (including removal of supported encodings). If
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you need your stuff to work correctly - start using UTF-8.
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## Configuration files
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maddy configuration files are assumed to be encoded in UTF-8. Use of any other
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encoding will break stuff, do not do it.
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Domain names (e.g. in hostname directive or pipeline rules) can be represented
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using the ACE form (aka Punycode). They will be converted to the Unicode form
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internally.
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## Local credentials
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'sql' storage backend and authentication provider enforce a number of additional
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constraints on used account names.
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PRECIS UsernameCaseMapped profile is enforced for local email addresses.
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It limits the use of control and Bidi characters to make sure the used value
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can be represented consistently in a variety of contexts. On top of that, the
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address is case-folded and normalized to the NFC form for consistent internal
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handling.
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PRECIS OpaqueString profile is enforced for passwords. Less strict rules are
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applied here. Runs of Unicode whitespace characters are replaced with a single
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ASCII space. NFC normalization is applied afterwards. If the resulting string
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is empty - the password is not accepted.
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Both profiles are defined in RFC 8265, consult it for details.
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## Protocol support
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### SMTPUTF8 extension
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maddy SMTP implementation includes support for the SMTPUTF8 extension as
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defined in RFC 6531.
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This means maddy can handle internationalized mailbox and domain names in MAIL
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FROM, RCPT TO commands both for outbound and inbound delivery.
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maddy will not accept messages with non-ASCII envelope addresses unless
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SMTPUTF8 support is requested. If a message with SMTPUTF8 flag set is forwarded
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to a server without SMTPUTF8 support, delivery will fail unless it is possible
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to represent envelope addresses in the ASCII form (only domains use Unicode and
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they can be converted to Punycode). Contents of message body (and header) are
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not considered and always accepted and sent as-is, no automatic downgrading or
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reencoding is done.
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### IMAP UTF8, I18NLEVEL extensions
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Currently, maddy does not include support for UTF8 and I18NLEVEL IMAP
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extensions. However, it is not a problem that can prevent it from correctly
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handling UTF-8 messages (or even messages in other non-ASCII encodings
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mentioned above).
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Clients that want to implement proper handling for Unicode strings may assume
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maddy does not handle them properly in e.g. SEARCH commands and so such clients
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may download messsages and process them locally.
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