Bug#821830: exim4: Exim rejects mail with overlong lines without any explanation

[Francesco Potortì]

Package: exim4
Version: 4.87-1
Severity: normal

I use Exim to get mail from Fetchmail.  In the last days I have lost
some mails and got unsubscribed from some mailing lists.  After much
digging, I discovered that an ACL rule has now been added which limits
line length to 998.

There are several problems here.

1) mail is rejected without any explanation; as a non-expert of Exim, it
   took me much digging to discover that an ACL rule exists which
   rejects mail without any explanation added to the logs: as a minimum,
   a message line should be added to the acl rule

2) this change is very important, as it can cause people to lose mail:
   the administrator should be clearly notified of it upon upgrade

3) there should be an easy way to disable the new behaviour, in the form
   of a configuration macro

4) apparently people around there send legitimate email with overlong
   lines.  Since Exim does not suffer from it, it should apply Postel's
   law «be conservative in what you do, be liberal in what you accept
   from others»: mail should definitely not be rejected by default
   because it contains overlong lines

-- 
Francesco Potortì (ricercatore)        Voice:  +39.050.621.3058
ISTI - Area della ricerca CNR          Mobile: +39.348.8283.107
via G. Moruzzi 1, I-56124 Pisa         Skype:  wnlabisti
(entrance 20, 1st floor, room C71)     Web:    http://fly.isti.cnr.it



-- Package-specific info:
Exim version 4.87 #2 built 07-Apr-2016 17:26:59
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
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
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 replace
# the DEBCONFsomethingDEBCONF strings in the configuration template files.
#
# 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='smarthost'
dc_other_hostnames=''
dc_local_interfaces='127.0.0.1'
dc_readhost=''
dc_relay_domains=''
dc_minimaldns='false'
dc_relay_nets=''
dc_smarthost='smtp.isti.cnr.it::587'
CFILEMODE='644'
dc_use_split_config='true'
dc_hide_mailname='false'
dc_mailname_in_oh='true'
dc_localdelivery='mail_spool'
#dc_message_size_limit='50M'
mailname:tucano.isti.cnr.it

*** Reporter, please consider answering these questions, where appropriate ***

   * What led up to the situation?
   * What exactly did you do (or not do) that was effective (or
     ineffective)?
   * What was the outcome of this action?
   * What outcome did you expect instead?

*** End of the template - remove these template lines ***


-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'testing-proposed-updates'), (101, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.4.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=it_IT.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages exim4 depends on:
ii  debconf [debconf-2.0]  1.5.59
ii  exim4-base             4.87-1
ii  exim4-daemon-light     4.87-1

exim4 recommends no packages.

exim4 suggests no packages.

-- debconf information:
  exim4/drec: