Bug#849770: exim4: bogus reject response on overlong lines

[Adam Borowski]

Package: exim4
Version: 4.88-2
Severity: normal

Hi!
If an user agent attempts to send a mail containing lines longer than SMTP's
allowed max of 998 bytes (such as reportbug -- #849765), exim's response is
extremely unhelpful.

The user gets:
.----[ Mail delivery failed: returning message to sender ]
[-- Attachment #1 --]
[-- Type: text/plain, Encoding: 7bit, Size: 0.3K --]

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  kilobyte at angband.pl
  submit at bugs.debian.org

[-- Attachment #2 --]
[-- Type: message/delivery-status, Encoding: 7bit, Size: 0.2K --]

Reporting-MTA: dns; umbar.angband.pl

Action: failed
Final-Recipient: rfc822;submit at bugs.debian.org
Status: 5.0.0

Action: failed
Final-Recipient: rfc822;kilobyte at angband.pl
Status: 5.0.0

[-- Attachment #3 --]
[-- Type: text/rfc822-headers, Encoding: 7bit, Size: 0.6K --]

Return-path: <kilobyte at angband.pl>
Received: from kilobyte by umbar.angband.pl with local (Exim 4.88)
        (envelope-from <kilobyte at angband.pl>)
        id 1cN1mV-0003BB-EP; Fri, 30 Dec 2016 19:19:55 +0100
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
From: Adam Borowski <kilobyte at angband.pl>
To: Debian Bug Tracking System <submit at bugs.debian.org>
Subject: mutt: complains about GPGME
Message-ID: <148312199535.12156.10016894553068573730.reportbug at umbar.angband.pl>
X-Mailer: reportbug 7.1.1
Date: Fri, 30 Dec 2016 19:19:55 +0100
X-Exim-DSN-Information: Due to administrative limits only headers are returned
`----

while the log entry is:
2016-12-30 19:19:55 1cN1mV-0003BB-EP <= kilobyte at angband.pl U=kilobyte P=local S=7284 id=148312199535.12156.10016894553068573730.reportbug at umbar.angband.pl
2016-12-30 19:19:55 1cN1mV-0003BB-EP ** submit at bugs.debian.org R=smarthost T=remote_smtp_smarthost: message is too big (transport limit = 1)
2016-12-30 19:19:55 1cN1mV-0003BB-EP ** kilobyte at angband.pl R=smarthost T=remote_smtp_smarthost: message is too big (transport limit = 1)

All of these machines use exim:
My desktop (umbar.angband.pl) has unstable: 4.88-2
My mail server (tartarus.angband.pl) has stretch: 4.88~RC6-2
b.d.o MX (buxtehude.debian.org) has jessie: 4.84_2 (probably 4.84.2-2+deb8u1)


The rejection message to the user, which needs to include information about
why the mail was rejected, says just "failed".

The log message is outright wrong: "message is too big" clearly means the
whole mail rather than just a single line.


-- Package-specific info:
Exim version 4.88 #2 built 27-Dec-2016 16:36:29
Copyright (c) University of Cambridge, 1995 - 2016
(c) The Exim Maintainers and contributors in ACKNOWLEDGMENTS file, 2007 - 2016
Berkeley DB: Berkeley DB 5.3.28: (September  9, 2013)
Support for: crypteq iconv() IPv6 GnuTLS move_frozen_messages DKIM DNSSEC Event OCSP PRDR SOCKS TCP_Fast_Open
Lookups (built-in): lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmjz dbmnz dnsdb dsearch nis nis0 passwd
Authenticators: cram_md5 plaintext
Routers: accept dnslookup ipliteral manualroute queryprogram redirect
Transports: appendfile/maildir/mailstore autoreply lmtp pipe smtp
Fixed never_users: 0
Configure owner: 0:0
Size of off_t: 8
Configuration file is /var/lib/exim4/config.autogenerated
# /etc/exim4/update-exim4.conf.conf
#
# Edit this file and /etc/mailname by hand and execute update-exim4.conf
# yourself or use 'dpkg-reconfigure exim4-config'
#
# Please note that this is _not_ a dpkg-conffile and that automatic changes
# to this file might happen. The code handling this will honor your local
# changes, so this is usually fine, but will break local schemes that mess
# around with multiple versions of the file.
#
# update-exim4.conf uses this file to determine variable values to generate
# exim configuration macros for the configuration file.
#
# Most settings found in here do have corresponding questions in the
# Debconf configuration, but not all of them.
#
# This is a Debian specific file

dc_eximconfig_configtype='satellite'
dc_other_hostnames='umbar.angband.pl'
dc_local_interfaces='127.0.0.1 ; ::1'
dc_readhost='angband.pl'
dc_relay_domains=''
dc_minimaldns='false'
dc_relay_nets=''
dc_smarthost='mail.angband.pl'
CFILEMODE='644'
dc_use_split_config='false'
dc_hide_mailname='true'
dc_mailname_in_oh='true'
dc_localdelivery='maildir_home'
mailname:umbar.angband.pl

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (500, 'testing'), (150, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0+ (SMP w/6 CPU cores)
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)

Versions of packages exim4 depends on:
ii  debconf [debconf-2.0]  1.5.59
ii  exim4-base             4.88-2
ii  exim4-daemon-light     4.88-2

exim4 recommends no packages.

exim4 suggests no packages.

-- debconf information:
  exim4/drec: