https://bugs.exim.org/show_bug.cgi?id=2979
Bug ID: 2979
Summary: Long SMTP response can result in deliverable bounce
Product: Exim
Version: 4.95
Hardware: All
OS: All
Status: NEW
Severity: bug
Priority: medium
Component: Delivery in general
Assignee: unallocated@???
Reporter: jgh146exb@???
CC: exim-dev@???
Reported in 1684, but tracking here as a separate bug.
A long SMTP error response, from end-of-data in the report,
resulted in a bounce message that exceeded it's transport's limit on
line length.
Log sequence:
2023-02-16 10:36:25 1pSagd-006b9M-2u <= <> H=SENDER I=INTERFACE P=esmtp S=1747
for SRS_ENCODED_RECIPIENT
2023-02-16 10:42:05 1pSagd-006b9M-2u ** SRS_DECODED_RECIPIENT
<SRS_ENCODED_RECIPIENT> P=<> R=dnslookup T=remote_forwarded_smtp H=SENDER
I=INTERFACE X=CERTIFICATE_INFO: SMTP error from remote mail server after
pipelined end of data: 550-Rejected spam (score 5.7): Content analysis
details:\n550-* -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at\n550-*
https://www.dnswl.org/, no trust\n550-* [ANON_IP listed in
list.dnswl.org]\n550-* 0.8 BAYES_50 BODY: Bayes spam probability is 40 to
60%\n550-* [score: 0.5000]\n550-* 0.1 DKIM_SIGNED Message has a DKIM or
DK signature, not necessarily\n550-* valid\n550-* -0.1 DKIM_VALID Message
has at least one valid DKIM or DK signature\n550-* 0.5 MISSING_MID Missing
Message-Id: header\n550-* 1.4 MISSING_DATE Missing Date: header\n550-* 3.0
MPI_OWN_HEADDOM_WO_DKIM mail with one of our domains in From\n550-* header
but no DKIM signature
found\n550--------------------------------------------------------------------------------\n550
* 05.7 Total Score DT=2s
2023-02-16 10:42:05 1pSagd-006b9M-2u Frozen (delivery error message)
2023-02-16 10:46:45 1pSagd-006b9M-2u removed by root
2023-02-16 10:46:45 1pSagd-006b9M-2u Completed
2023-02-16 10:42:05 1pSamD-006e0P-1E <= <> R=1pSagd-006b9M-2u U=Debian-exim
P=local S=1533 for postmaster
2023-02-16 10:42:05 1pSamD-006e0P-1E ** POSTMASTER_ALIAS_ADDRESS
<POSTMASTER_ADDRESS> P=<> R=local_user T=dovecot: message has lines too long
for transport DT=0s
2023-02-16 10:42:05 1pSamD-006e0P-1E Frozen (delivery error message)
2023-02-16 10:47:02 1pSamD-006e0P-1E Message is frozen
2023-02-16 10:48:55 1pSamD-006e0P-1E removed by root
2023-02-16 10:48:55 1pSamD-006e0P-1E Completed
>From examination of source so far, this only applies when compiled with
EXPERIMENTAL_DSN_INFO defined.
We don't have access to the specific transport for the bounce, in the
code generating the bounce - routing it not having been done yet -
so cannot know what limits it will apply.
However, splitting a multiline response (this one was), which was
munged for logging, seems obvious. We might also consider deliberate
wrapping at word boundaries when exceeding an 80-char line.
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