https://bugzilla.wikimedia.org/show_bug.cgi?id=19001

Philippe Verdy <verd...@wanadoo.fr> changed:

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--- Comment #3 from Philippe Verdy <verd...@wanadoo.fr> 2010-10-10 10:25:16 UTC 
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This is NOT a bug, but the standard way to encode emails subject lines, when it
does not contain only ASCII characters (here, this uses the Quoted-Printable
encoding to indicate how to interpret the email subject line, only to specify
that its encoded bytes must be decoded with UTF-8 and not with another charset
(which cannot be specified anywhere else, given that historically the subject
lines was only supporting ASCII).

Note that the email body is encoded separately with another email header (the
"Mime-Type:" header) which applies ONLY to the email body (which does not need
Quoted-Printable or Base-64 transport syntax as almost all SMTP and POP3
servers used today are 8-bit clean, as well as all IMAP servers.

Remember that throughout SMTP email headers, only the ASCII subset is safe
(that's why the Quoted-Printable and Base-64 is still used today). Ideally,
they should be 8-bit clean too, but there's still no standard way to specify
which encoding is effectively used in the email subject line, notably because
the Subject line is NOT sent to SMTP servers using MIME headers, but within
SMTP command-lines that are still NOT 8-bit clean (there are still a lot of
SMTP servers deployed worlwide (including from major ISPs) using the older RFCs
for this protocol, and not its the ESMTP revision (they are afraid to deploy
ESMTP due to possible additional security risks).

Note that it is IMPOSSIBLE to safely determine if the target SMTP server
understands the ESMTP protocol or is 8-bit clean before starting a negociation,
and most SMTP servers do not support negociation of the protocol (emails can
only be sent in a single request that will be accepted or rejected immediately
without explaining in a machine-readable response why this failed, and any
failure will generally cause the SMTP server to close the connection
immediately).

If your email agent does not support the standard Quoted-Printable (or Base64)
encoding with this markup in the emails you receive, change it or upgrade it,
as it is really out of date and does not support standard MIME RFC's.

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