Docker-mailserver: Helo command rejected: Invalid name

[InsOpDe]

Mailserve works properly but not under following circumstitions:
Helo command gets rejected when I try to send an mail via mailserver which is in a VM in google cloud.

Context

I have a Kubernetes cluster with one pod trying to send a mail via the mailserver. Same credentials work with my thunderbird client.

Expected Behavior

Should connect

Actual Behavior

Does not connect

Your Environment

• .env

# -----------------------------------------------------------------------------------------------------------------------------
# --------------------- General Settings --------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

HOSTNAME=mail
DOMAINNAME=example.com
CONTAINER_NAME=mail

# empty => uses the `hostname` command to get the mail server's canonical hostname
# => Specify a fully-qualified domainname to serve mail for.  This is used for many of the config features so if you can't set your hostname (e.g. you're in a container platform that doesn't let you) specify it in this environment variable.
OVERRIDE_HOSTNAME=

# 0 => Debug disabled
# 1 => Enables debug on startup
DMS_DEBUG=0

# 0 => mail state in default directories
# 1 => consolidate all states into a single directory (`/var/mail-state`) to allow persistence using docker volumes
ONE_DIR=0

# empty => [email protected]
# => Specify the postmaster address
[email protected]

# Set different options for mynetworks option (can be overwrite in postfix-main.cf)
# empty => localhost only
# host => Add docker host (ipv4 only)
# network => Add all docker containers (ipv4 only)
PERMIT_DOCKER=

# empty => modern
# modern => Enables TLSv1.2 and modern ciphers only. (default)
# intermediate => Enables TLSv1, TLSv1.1 and TLSv1.2 and broad compatibility ciphers.
# old => NOT implemented. If you really need it, then customize the TLS ciphers overriding postfix and dovecot settings
#        (https://github.com/tomav/docker-mailserver/wiki/)
TLS_LEVEL=

# Configures the handling of creating mails with forged sender addresses.
#
# empty => (not recommended, but default for backwards compatability reasons)
#           Mail address spoofing allowed. Any logged in user may create email messages with a forged sender address.
#           See also https://en.wikipedia.org/wiki/Email_spoofing
# 1 => (recommended) Mail spoofing denied. Each user may only send with his own or his alias addresses.
#       Addresses with extension delimiters(http://www.postfix.org/postconf.5.html#recipient_delimiter) are not able to send messages.
SPOOF_PROTECTION=1

# Enables the Sender Rewriting Scheme. SRS is needed if your mail server acts as forwarder. See [postsrsd](https://github.com/roehling/postsrsd/blob/master/README.md#sender-rewriting-scheme-crash-course) for further explanation.
#  - **0** => Disabled
#  - 1 => Enabled
ENABLE_SRS=0

# 1 => Enables POP3 service
# empty => disables POP3
ENABLE_POP3=
ENABLE_CLAMAV=0

# If you enable Fail2Ban, don't forget to add the following lines to your `docker-compose.yml`:
#    cap_add:
#      - NET_ADMIN
# Otherwise, `iptables` won't be able to ban IPs.
ENABLE_FAIL2BAN=0

# 1 => Enables Managesieve on port 4190
# empty => disables Managesieve
ENABLE_MANAGESIEVE=

# **enforce** => Allow other tests to complete. Reject attempts to deliver mail with a 550 SMTP reply, and log the helo/sender/recipient information. Repeat this test the next time the client connects.
# drop => Drop the connection immediately with a 521 SMTP reply. Repeat this test the next time the client connects.
# ignore => Ignore the failure of this test. Allow other tests to complete. Repeat this test the next time the client connects. This option is useful for testing and collecting statistics without blocking mail.
POSTSCREEN_ACTION=enforce

# empty => all daemons start
# 1 => only launch postfix smtp
SMTP_ONLY=

# Please read [the SSL page in the wiki](https://github.com/tomav/docker-mailserver/wiki/Configure-SSL) for more information.
#
# empty => SSL disabled
# letsencrypt => Enables Let's Encrypt certificates
# custom => Enables custom certificates
# manual => Let's you manually specify locations of your SSL certificates for non-standard cases
# self-signed => Enables self-signed certificates
SSL_TYPE=letsencrypt

# Set how many days a virusmail will stay on the server before being deleted
# empty => 7 days
VIRUSMAILS_DELETE_DELAY=

# This Option is activating the Usage of POSTFIX_DAGENT to specify a ltmp client different from default dovecot socket.
# empty => disabled
# 1 => enabled
ENABLE_POSTFIX_VIRTUAL_TRANSPORT=

# Enabled by ENABLE_POSTFIX_VIRTUAL_TRANSPORT. Specify the final delivery of postfix
#
# empty => fail
# `lmtp:unix:private/dovecot-lmtp` (use socket)
# `lmtps:inet:<host>:<port>` (secure lmtp with starttls, take a look at https://sys4.de/en/blog/2014/11/17/sicheres-lmtp-mit-starttls-in-dovecot/)
# `lmtp:<kopano-host>:2003` (use kopano as mailstore)
# etc.
POSTFIX_DAGENT=

# Set the mailbox size limit for all users. If set to zero, the size will be unlimited (default).
#
# empty => 0
POSTFIX_MAILBOX_SIZE_LIMIT=

# Set the message size limit for all users. If set to zero, the size will be unlimited (not recommended!)
# 
# empty => 10240000 (~10 MB)
POSTFIX_MESSAGE_SIZE_LIMIT= 102400000

# Enables a report being sent (created by pflogsumm) on a regular basis.
# **0** => Report emails are disabled
# 1 => Using POSTMASTER_ADDRESS as the recipient
# => Specify the recipient address
REPORT_RECIPIENT=0


# Change the sending address for mail report
# **empty** => mailserver-report@hostname
# => Specify the report sender (From) address
REPORT_SENDER=

# Changes the interval in which a report is being sent.
# **daily** => Send a daily report
# weekly => Send a report every week
# monthly => Send a report every month
#
# Note: This Variable actually controls logrotate inside the container and rotates the log depending on this setting. The main log output is still available in its entirety via `docker logs mail` (Or your respective container name). If you want to control logrotation for the docker generated logfile see: [Docker Logging Drivers](https://docs.docker.com/config/containers/logging/configure/)
REPORT_INTERVAL=daily

# -----------------------------------------------------------------------------------------------------------------------------
# --------------------- Spamassassin section ----------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

ENABLE_SPAMASSASSIN=0

# add spam info headers if at, or above that level:
SA_TAG=2.0

# add 'spam detected' headers at that level
SA_TAG2=6.31

# triggers spam evasive actions
SA_KILL=6.31

# add tag to subject if spam detected
SA_SPAM_SUBJECT=***SPAM*****

# -----------------------------------------------------------------------------------------------------------------------------
# --------------------- Fetchmail section -------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

ENABLE_FETCHMAIL=0

# The interval to fetch mail in seconds
FETCHMAIL_POLL=300

# -----------------------------------------------------------------------------------------------------------------------------
# --------------------- LDAP section ------------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

# A second container for the ldap service is necessary (i.e. https://github.com/osixia/docker-openldap)
# For preparing the ldap server to use in combination with this container this article may be helpful: http://acidx.net/wordpress/2014/06/installing-a-mailserver-with-postfix-dovecot-sasl-ldap-roundcube/

# empty => LDAP authentification is disabled
# 1 => LDAP authentification is enabled
ENABLE_LDAP=

# empty => no
# yes => LDAP over TLS enabled for Postfix
LDAP_START_TLS=

# If you going to use the mailserver in combination with docker-compose you can set the service name here
# empty => mail.domain.com
# Specify the dns-name/ip-address where the ldap-server
LDAP_SERVER_HOST=

# empty => ou=people,dc=domain,dc=com
# => e.g. LDAP_SEARCH_BASE=dc=mydomain,dc=local
LDAP_SEARCH_BASE=

# empty => cn=admin,dc=domain,dc=com
# => take a look at examples of SASL_LDAP_BIND_DN
LDAP_BIND_DN=

# empty** => admin
# => Specify the password to bind against ldap
LDAP_BIND_PW=

# e.g. `"(&(mail=%s)(mailEnabled=TRUE))"`
# => Specify how ldap should be asked for users
LDAP_QUERY_FILTER_USER=

# e.g. `"(&(mailGroupMember=%s)(mailEnabled=TRUE))"`
# => Specify how ldap should be asked for groups
LDAP_QUERY_FILTER_GROUP=

# e.g. `"(&(mailAlias=%s)(mailEnabled=TRUE))"`
# => Specify how ldap should be asked for aliases
LDAP_QUERY_FILTER_ALIAS=

# -----------------------------------------------------------------------------------------------------------------------------
# ---------------- Dovecot section --------------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

# empty => no
# yes => LDAP over TLS enabled for Dovecot
DOVECOT_TLS=

# e.g. `"(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))"`
DOVECOT_USER_FILTER=

# e.g. `"(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))"`
DOVECOT_PASS_FILTER=

# -----------------------------------------------------------------------------------------------------------------------------
# ---------------- Postgrey section -------------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

ENABLE_POSTGREY=0
# greylist for N seconds
POSTGREY_DELAY=300
# delete entries older than N days since the last time that they have been seen
POSTGREY_MAX_AGE=35
# response when a mail is greylisted
POSTGREY_TEXT=Delayed by postgrey

# -----------------------------------------------------------------------------------------------------------------------------
# ---------------- SASL section -----------------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

ENABLE_SASLAUTHD=0

# empty => pam
# `ldap` => authenticate against ldap server
# `shadow` => authenticate against local user db
# `mysql` => authenticate against mysql db
# `rimap` => authenticate against imap server
# NOTE: can be a list of mechanisms like pam ldap shadow
SASLAUTHD_MECHANISMS=

# empty => None
# e.g. with SASLAUTHD_MECHANISMS rimap you need to specify the ip-address/servername of the imap server  ==> xxx.xxx.xxx.xxx
SASLAUTHD_MECH_OPTIONS=

# empty => localhost
SASLAUTHD_LDAP_SERVER=

# empty or 0 => `ldap://` will be used
# 1 => `ldaps://` will be used
SASLAUTHD_LDAP_SSL=

# empty => anonymous bind
# specify an object with priviliges to search the directory tree
# e.g. active directory: SASLAUTHD_LDAP_BIND_DN=cn=Administrator,cn=Users,dc=mydomain,dc=net
# e.g. openldap: SASLAUTHD_LDAP_BIND_DN=cn=admin,dc=mydomain,dc=net
SASLAUTHD_LDAP_BIND_DN=

# empty => anonymous bind
SASLAUTHD_LDAP_PASSWORD=

# empty => Reverting to SASLAUTHD_MECHANISMS pam
# specify the search base
SASLAUTHD_LDAP_SEARCH_BASE=

# empty => default filter `(&(uniqueIdentifier=%u)(mailEnabled=TRUE))`
# e.g. for active directory: `(&(sAMAccountName=%U)(objectClass=person))`
# e.g. for openldap: `(&(uid=%U)(objectClass=person))`
SASLAUTHD_LDAP_FILTER=

# empty => no
# yes => LDAP over TLS enabled for SASL
# Must not be used together with SASLAUTHD_LDAP_SSL=1_
SASLAUTHD_LDAP_START_TLS=

# empty => no
# yes => Require and verify server certificate
SASLAUTHD_LDAP_TLS_CHECK_PEER=

# empty => No sasl_passwd will be created
# string => `/etc/postfix/sasl_passwd` will be created with the string as password
SASL_PASSWD=

# -----------------------------------------------------------------------------------------------------------------------------
# ---------------- SRS section --------------------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

# empty => Envelope sender will be rewritten for all domains
# provide comma separated list of domains to exclude from rewriting
SRS_EXCLUDE_DOMAINS=

# empty => generated when the image is built
# provide a secret to use in base64
# you may specify multiple keys, comma separated. the first one is used for
# signing and the remaining will be used for verification. this is how you
# rotate and expire keys
SRS_SECRET=

# -----------------------------------------------------------------------------------------------------------------------------
# ---------------- Multi-domain relay section ---------------------------------------------------------------------------------
# -----------------------------------------------------------------------------------------------------------------------------

# Setup relaying for multiple domains based on the domain name of the sender
# optionally uses usernames and passwords in postfix-sasl-password.cf and relay host mappings in postfix-relaymap.cf
#
# empty => don't configure relay host
# default host to relay mail through
RELAY_HOST=

# empty => 25
# default port to relay mail
RELAY_PORT=25

# empty => no default
# default relay username (if no specific entry exists in postfix-sasl-password.cf)
RELAY_USER=

# empty => no default
# password for default relay user
RELAY_PASSWORD=

• Logs from mailserver

mail    | Sep 16 12:48:56 mail postfix/submission/smtpd[7565]: connect from 84.205.247.35.bc.googleusercontent.com[35.246.205.94]
mail    | Sep 16 12:48:56 mail postfix/submission/smtpd[7326]: lost connection after RSET from 84.205.247.35.bc.googleusercontent.com[35.246.205.94]
mail    | Sep 16 12:48:56 mail postfix/submission/smtpd[7326]: disconnect from 84.205.247.35.bc.googleusercontent.com[35.246.205.94] ehlo=2 starttls=1 auth=1 mail=1 rcpt=0/1 rset=1 commands=6/7
mail    | Sep 16 12:48:56 mail postfix/submission/smtpd[7565]: Anonymous TLS connection established from 84.205.247.35.bc.googleusercontent.com[35.246.205.94]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
mail    | Sep 16 12:48:56 mail postfix/submission/smtpd[7565]: NOQUEUE: reject: RCPT from 84.205.247.35.bc.googleusercontent.com[35.246.205.94]: 501 5.5.2 <600>: Helo command rejected: Invalid name; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<600>         

* I have redacted personal information mostly with the example.com-host *

[erik-wramner]

I think the error is in the code that tries to send e-mail. Postfix is configured to insist on a valid host name in the initial HELO/EHLO command. It complains that the host name was empty. Perhaps your mail client doesn't provide one? Thunderbird probably follows the e-mail protocol to the letter, but custom code often takes shortcuts.

[InsOpDe]

i am using https://github.com/janeczku/calibre-web to send mails and have no insights into how the mail gets sent. Is there a way to disable this requirement of postfix, so that I can verify this assumption?

[erik-wramner]

Well, I'm not an expert in Postfix, but there are two options that may do the job: smtpd_helo_restrictions and smtpd_helo_required. Google about them. I haven't tested, but I think you can override them in docker-mailserver by adding them to your config/postfix-main.cf file:

smtpd_helo_required=no
smtpd_helo_restrictions=

You need to run docker-compose down and up. See if it helps. If it doesn't it may be because the options didn't take or you may have run into another error.

[InsOpDe]

Thanks that worked. I close this now as this isnt a problem with this repository.