Thunderbird: Improper command pipelinig after EHLO

bdimitrov

Hey everyone,

I’d like to ask for your help with an issue I’m encountering.

I’m currently setting up grommunio, and during the installation and configuration process I repeatedly run into a problem that prevents me from completing the setup.

I keep seeing the following log entries:
Feb 07 22:58:49 bwsu-b-mail01a postfix/submissions/smtpd[18002]: Read 27 chars: EHLO we-guess.mozilla.org?? Feb 07 23:37:02 bwsu-b-mail01a postfix/submissions/smtpd[18425]: Read 27 chars: EHLO we-guess.mozilla.org?? Feb 07 23:37:07 bwsu-b-mail01a postfix/submissions/smtpd[18425]: Read 27 chars: EHLO we-guess.mozilla.org?? Feb 08 00:13:54 bwsu-b-mail01a postfix/submissions/smtpd[18858]: Read 33 chars: EHLO we-guess.mozilla.org??QUIT??
Additionally, I see messages like:improper command pipelining after EHLO from unknown[pub-ip]: QUIT\r\n
and also
mproper command pipelining after CONNECT from unknown[pub-ip]: \026\003\001\aZ\001\000\aV\003\003u(g\343\217q\t/\255\212\236\205\b~\261\033\3438)O\370\177\265\241\314|\267\225#4v\037 \317\367^A\320AJy&\260N\323\333Y\n%\b@i\270\260/\344\205Q\315\204\031<p\346\005\000"\023\001\023\003\023\002\300+\300/\314\251\314\250\300,\3000\300\n\300\t

SMTP authentication is handled via saslauthd (PAM), which in turn forwards authentication to the gromox auth-manager (LDAP in my case).

If I disable unauthenticated pipelining checks, everything works as expected. However, based on the documentation and recommendations, it seems preferable to keep the default behavior enabled.

Below are the relevant excerpts from my main.cf and master.cf configurations for reference.

main.cf

##### server settings
compatibility_level = 3.9
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
biff = no
# IP protocols to use: ipv4, ipv6, or all
# (set this explicitly so `post-install upgrade-configuration' wont complain)
#recieve mail, this case from pmmg
inet_interfaces = all
#ipv4/ipv6 or all
inet_protocols = all
myhostname= bwsu-b-mail01a.domain.com
mydestination = $myhostname mail.$myhostname localhost.$mydomain localhost

mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 10.2.1.54
virtual_alias_maps = mysql:/etc/postfix/grommunio-virtual-mailbox-alias-maps.cf
virtual_mailbox_domains = mysql:/etc/postfix/grommunio-virtual-mailbox-domains.cf
virtual_mailbox_maps = mysql:/etc/postfix/grommunio-virtual-mailbox-maps.cf
virtual_transport = smtp:[localhost]:24
##smtpd settings
#smtpd_data_restrictions = reject_unauth_pipelining
smtpd_helo_restrictions = permit_mynetworks,permit_sasl_authenticated,reject_invalid_hostname,reject_non_fqdn_hostname
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unknown_recipient_domain,reject_non_fqdn_hostname,reject_non_fqdn_sender,reject_non_fqdn_recipient,reject_unauth_destination
smtpd_sender_restrictions = reject_non_fqdn_sender,permit_sasl_authenticated,permit_mynetworks

##tls req
smtpd_tls_received_header = yes
smtpd_tls_security_level = may
smtpd_tls_session_cache_timeout = 3600s
broken_sasl_auth_clients = yes
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_tls_security_options = noanonymous
cyrus_sasl_config_path = /etc/postfix/sasl
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_path = smtpd
smtpd_sasl_type = cyrus


##tsl
smtp_tls_key_file = /etc/postfix/smtpd.key
smtp_tls_cert_file = /etc/postfix/smtpd.pem
smtpd_tls_key_file = /etc/postfix/smtpd.key
smtpd_tls_cert_file = /etc/postfix/smtpd.pem
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_protocols = !SSLv2,!SSLv3
smtp_tls_protocols = !SSLv2,!SSLv3

smtp_tls_security_level = may

##logging 
smtpd_tls_loglevel = 4
debug_peer_level = 2
maillog_file = /var/log/mail.log
maillog_file_permissions = 0644

#alias test
# List of alias maps to use to lookup local addresses.
# Per Debian Policy it should be /etc/aliases.
alias_maps = hash:/etc/aliases
# List of alias maps to make indexes on, when running newaliases.
alias_database = hash:/etc/aliases


#testing 
smtpd_sender_login_maps = mysql:/etc/postfix/grommunio-virtual-mailbox-maps.cf,mysql:/etc/postfix/grommunio-virtual-mailbox-alias-maps.cf 
smtpd_helo_required = yes
smtpd_helo_restrictions=permit_mynetworks,permit_sasl_authenticated,reject_invalid_hostname,reject_non_fqdn_hostname

master.cf

# Postfix master process configuration file.  For details on the format
# of the file, see the master(5) manual page (command: "man 5 master" or
# on-line: https://www.postfix.org/master.5.html).
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ==========================================================================
# service type  private unpriv  chroot  wakeup  maxproc command + args
#               (yes)   (yes)   (no)    (never) (100)
# ==========================================================================
smtp      inet  n       -       y       -       -       smtpd
#smtp      inet  n       -       y       -       1       postscreen
#smtpd     pass  -       -       y       -       -       smtpd
#dnsblog   unix  -       -       y       -       0       dnsblog
#tlsproxy  unix  -       -       y       -       0       tlsproxy
# Choose one: enable submission for loopback clients only, or for any client.
#127.0.0.1:submission inet n -   y       -       -       smtpd
submission inet n       -       n       -       -       smtpd
  -o syslog_name=postfix/submission
#  -o smtpd_forbid_unauth_pipelining=no
  -o smtpd_tls_security_level=encrypt
  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_tls_auth_only=yes
#  -o local_header_rewrite_clients=static:all
#  -o smtpd_hide_client_session=yes
#  -o smtpd_reject_unlisted_recipient=no
#     Instead of specifying complex smtpd_<xxx>_restrictions here,
#     specify "smtpd_<xxx>_restrictions=$mua_<xxx>_restrictions"
#     here, and specify mua_<xxx>_restrictions in main.cf (where
#     "<xxx>" is "client", "helo", "sender", "relay", or "recipient").
#  -o smtpd_client_restrictions=
#  -o smtpd_helo_restrictions=
#  -o smtpd_sender_restrictions=
#  -o smtpd_data_restrictions=
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
 # -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
 # -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
# Choose one: enable submissions for loopback clients only, or for any client.
#127.0.0.1:submissions inet n  -       y       -       -       smtpd
submissions     inet  n       -       n       -       -       smtpd
  -o syslog_name=postfix/submissions
#  -o smtpd_forbid_unauth_pipelining=no
  -o smtpd_tls_security_level=encrypt
  -o smtpd_tls_wrappermode=yes
#  -o smtpd_data_restrictions=
  -o smtpd_sasl_auth_enable=yes
#  -o local_header_rewrite_clients=static:all
#  -o smtpd_hide_client_session=yes
#  -o smtpd_reject_unlisted_recipient=no
#     Instead of specifying complex smtpd_<xxx>_restrictions here,
#     specify "smtpd_<xxx>_restrictions=$mua_<xxx>_restrictions"
#     here, and specify mua_<xxx>_restrictions in main.cf (where
#     "<xxx>" is "client", "helo", "sender", "relay", or "recipient").
#  -o smtpd_client_restrictions=
#  -o smtpd_helo_restrictions=
#  -o smtpd_sender_restrictions=
  #-o smtpd_client_restrictions=permit_sasl_authenticated,reject
  #-o smtpd_relay_restrictions=permit_sasl_authenticated,reject
  #-o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#628       inet  n       -       y       -       -       qmqpd
pickup    unix  n       -       y       60      1       pickup
cleanup   unix  n       -       y       -       0       cleanup
qmgr      unix  n       -       n       300     1       qmgr
#qmgr     unix  n       -       n       300     1       oqmgr
tlsmgr    unix  -       -       y       1000?   1       tlsmgr
rewrite   unix  -       -       y       -       -       trivial-rewrite
bounce    unix  -       -       y       -       0       bounce
defer     unix  -       -       y       -       0       bounce
trace     unix  -       -       y       -       0       bounce
verify    unix  -       -       y       -       1       verify
flush     unix  n       -       y       1000?   0       flush
proxymap  unix  -       -       n       -       -       proxymap
proxywrite unix -       -       n       -       1       proxymap
smtp      unix  -       -       y       -       -       smtp
relay     unix  -       -       y       -       -       smtp
        -o syslog_name=${multi_instance_name?{$multi_instance_name}:{postfix}}/$service_name
#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq     unix  n       -       y       -       -       showq
error     unix  -       -       y       -       -       error
retry     unix  -       -       y       -       -       error
discard   unix  -       -       y       -       -       discard
local     unix  -       n       n       -       -       local
virtual   unix  -       n       n       -       -       virtual
lmtp      unix  -       -       y       -       -       lmtp
anvil     unix  -       -       y       -       1       anvil
scache    unix  -       -       y       -       1       scache
postlog   unix-dgram n  -       n       -       1       postlogd
#
# ====================================================================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.
#
# Many of the following services use the Postfix pipe(8) delivery
# agent.  See the pipe(8) man page for information about ${recipient}
# and other message envelope options.
# ====================================================================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
#maildrop  unix  -       n       n       -       -       pipe
#  flags=DRXhu user=vmail argv=/usr/bin/maildrop -d ${recipient}
#
# ====================================================================
#
# Recent Cyrus versions can use the existing "lmtp" master.cf entry.
#
# Specify in cyrus.conf:
#   lmtp    cmd="lmtpd -a" listen="localhost:lmtp" proto=tcp4
#
# Specify in main.cf one or more of the following:
#  mailbox_transport = lmtp:inet:localhost
#  virtual_transport = lmtp:inet:localhost
#
# ====================================================================
#
# Cyrus 2.1.5 (Amos Gouaux)
# Also specify in main.cf: cyrus_destination_recipient_limit=1
#
#cyrus     unix  -       n       n       -       -       pipe
#  flags=DRX user=cyrus argv=/cyrus/bin/deliver -e -r ${sender} -m ${extension} ${user}
#
# ====================================================================
#
# Old example of delivery via Cyrus.
#
#old-cyrus unix  -       n       n       -       -       pipe
#  flags=R user=cyrus argv=/cyrus/bin/deliver -e -m ${extension} ${user}
#
# ====================================================================
#
# See the Postfix UUCP_README file for configuration details.
#
#uucp      unix  -       n       n       -       -       pipe
#  flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# ====================================================================
#
# Other external delivery methods.
#
#ifmail    unix  -       n       n       -       -       pipe
#  flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
#
#bsmtp     unix  -       n       n       -       -       pipe
#  flags=Fq. user=bsmtp argv=/usr/lib/bsmtp/bsmtp -f $sender $nexthop $recipient
#
#scalemail-backend unix -       n       n       -       2       pipe
#  flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store
#  ${nexthop} ${user} ${extension}
#
#mailman   unix  -       n       n       -       -       pipe
#  flags=FRX user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
#  ${nexthop} ${user}

Thank you for your help in advance.

bdimitrov

After doing some research, this appears to be a known issue in Mozilla Thunderbird/Firefox that has not yet been fully resolved.
See the related bug report here:
https://bugzilla.mozilla.org/show_bug.cgi?id=538809

The reason this issue does not occur on some other systems is that, starting with Postfix version 3.9, the default setting for

smtpd_forbid_unauth_pipelining = yes

was changed to enabled by default, and this behavior has also been backported to older Postfix versions where it remains disabled.

Reference:
https://www.postfix.org/announcements/postfix-3.9.0.html

As a result, when using STARTTLS on port 587, Thunderbird may pipeline QUIT immediately after EHLO, which Postfix treats as a protocol violation and closes the connection.

To make this work reliably, you must either:

disable unauthenticated pipelining on the submission service, or

switch clients to implicit TLS on port 465 (which works, although the probing error may still appear in the logs).

Because this behavior originates from the client side, this issue should ideally be escalated to Mozilla.

I am marking this issue as resolved.