Wietse Venema via Postfix-users wrote in <4vstkr2gkhzj...@spike.porcupine.org>: |Steffen Nurpmeso via Postfix-users: |> Wietse Venema via Postfix-users wrote in |> <4vsq5f6q3nzj...@spike.porcupine.org>: |>|Tim Coote via Postfix-users: |> .. |>|> SMTP headers are often 'folded' as they flow through MTAs. The |>|> standard approach to folding and unfolding is covered in rfcs 5322 |> ... |>|3) Lines that exceed 998 bytes (not including <CR><LF>) cannot be |>| sent in SMTP. The result of sending such text is UNDEFINED. |> ... |>| When a line is too long, the Postfix SMTP client inserts |>| <CR><LF><SPACE> (controlled by smtp_line_length_limit). |> |> This is a deficit of the entire RFC *822 series that a superficial |> whitespace is necessary at that point. It was simply not on the |> table, and i got not even an answer on that in private |> communication (but maybe because of my way of speaking things out, |> i mean, isn't that just a desaster: this *breaks* the protocol). |> (On the other hand the dinosaur nmh just got (partially) proper |> line folding in September last year: |> |> http://git.savannah.gnu.org/cgit/nmh.git/commit/?id=542cb12b6d0646b7117\ |> 72ee97c1e2aacf2bada86 |> |> and they will fail for the artificial case as i said in |> |> https://lists.nongnu.org/archive/html/nmh-workers/2023-08/msg00010.html |> [https://lists.nongnu.org/archive/html/nmh-workers/2023-08/msg00011.htm\ |> l]) |> |>| Before Postfix inserted <CR><LF><SPACE>, some MTA would insert |>| a line break after ~1024 without adding a space. This would |>| "terminate" the message header, destroy the MIME structure, and |> |> This is really what they do? Then .. my "artificial whitespace" |> thought of a decade ago would be wrong. I would have thought they |> possibly reformat with RFC 2047 (if they can), as i said in the |> msg00011 thing above. | |Yes this was a real problem. | |For example, an email message like this: | | label: value | label: value-that exceeds-smtp-limit | ...zero or more label: value... | MIME-Version-1.0 | Content-type: multipart/mixed, boundary="foobar" | END_OF_PRIMARY_HEADER | | This is a multi-part message in MIME format. | | --foobar | first body part | | --foobar | first body part | | --foobar-- | |Was received as: | | label: value | label: value | label: first-part-of-value-that-exceeds-smtp-limit | END_OF_PRIMARY_HEADER | | first body line with remainder-of-value-that-exceeds-smtp-limit | |>From here on all remaining content including headers and MIME |boundaries was received as one large non-MIME message body and was |displayed to the user in its encoded form includeing MIME boundaries |encoded text (quoted-printable or base62 encoded). | |Why did that happen? Because some MTA's input reader did not know |if it was reading a header or body line.
Very interesting. All i knew until know is that there were quite some messages without separating empty line in between headers and body, "we" (the MUA i maintain) do a "find :" dance thus, and in the worst case add one. (This MUA comes from the 70s and still mostly thinks email==(single-message) MBOX.) --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt) _______________________________________________ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
