Subject
Incoming e-mails from external servers are not received.
Description
Hey there,
I recently installed your mailserver and it works pretty well.
The only problem I just cannot solve is the receival of incoming e-mails from external servers.
Intra-server mail transmission works fine though, so I think that the problem is somehow related to my DNS settings or maybe a misconfiguration of the mailserver (e.g. the hostname).
Listening on port 25 for inter-mailserver communication traffic results in this output directly after sending an e-mail from another e-mail domain to my mailserver domain.
Capturing on 'eth0'
1 0.000000000 40.92.75.97 → 75.119.129.6 TCP 66 15591 → 25 [SYN, ECN, CWR] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
2 0.000067356 75.119.129.6 → 40.92.75.97 TCP 54 25 → 15591 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
3 0.523886062 40.92.75.42 → 75.119.129.6 TCP 66 38734 → 25 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
4 0.523974447 75.119.129.6 → 40.92.75.42 TCP 54 25 → 38734 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
5 1.044128701 40.92.75.65 → 75.119.129.6 TCP 66 16822 → 25 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
6 1.044193733 75.119.129.6 → 40.92.75.65 TCP 54 25 → 16822 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
7 1.067185129 2a01:111:f400:fe0e::829 → 2a02:c206:3006:9356::1 TCP 86 30336 → 25 [SYN, ECN, CWR] Seq=0 Win=64800 Len=0 MSS=1440 WS=256 SACK_PERM=1
8 1.067225966 2a02:c206:3006:9356::1 → 2a01:111:f400:fe0e::829 TCP 74 25 → 30336 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
9 1.586858712 2a01:111:f400:fe0e::812 → 2a02:c206:3006:9356::1 TCP 86 12708 → 25 [SYN] Seq=0 Win=64800 Len=0 MSS=1440 WS=256 SACK_PERM=1
10 1.586903315 2a02:c206:3006:9356::1 → 2a01:111:f400:fe0e::812 TCP 74 25 → 12708 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
11 2.109182989 2a01:111:f400:fe0e::814 → 2a02:c206:3006:9356::1 TCP 86 63953 → 25 [SYN] Seq=0 Win=64800 Len=0 MSS=1440 WS=256 SACK_PERM=1
12 2.109227021 2a02:c206:3006:9356::1 → 2a01:111:f400:fe0e::814 TCP 74 25 → 63953 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0
However, no output is logged at the mailserver docker container and no e-mail is received.
After a few hours, an automatic mail with the following content is sent back to the sender e-mail address:
This is the mail system at host s252.goserver.host.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<[email protected]>: connect to mail.luckev.info[2a02:c206:3006:9356::1]:25:
Network is unreachable
Reporting-MTA: dns; s252.goserver.host
X-Postfix-Queue-ID: 3C56E156487B
X-Postfix-Sender: rfc822; [email protected]
Arrival-Date: Sat, 6 Mar 2021 15:18:10 +0100 (CET)
Final-Recipient: rfc822; [email protected]
Original-Recipient: rfc822;[email protected]
Action: failed
Status: 4.4.1
Diagnostic-Code: X-Postfix; connect to
mail.luckev.info[2a02:c206:3006:9356::1]:25: Network is unreachable
My DNS-Configuration (hosted by HostEurope) is the following:

The mailserver runs on a new server of Contabo with IPs 75.119.129.6 and 2a02:c206:3006:9356::1, hostname luckev.info and is supposed to serve mails for mail.luckev.info.
The docker-compose entry looks like this
version: '3'
services:
mail:
container_name: mail
image: mailserver/docker-mailserver:stable
hostname: mail
domainname: luckev.info
env_file: /var/data/mailserver/mailserver.env
ports:
- 25:25
- 143:143
- 587:587
- 993:993
restart: always
volumes:
- /var/data/mailserver/data:/var/mail
- /var/data/mailserver/state:/var/mail-state
- /var/data/mailserver/logs:/var/log/mail
- /var/data/mailserver/config:/tmp/docker-mailserver/
- /var/data/certbot/conf/live/luckev.info/fullchain.pem:/tmp/ssl/cert/public.crt:ro
- /var/data/certbot/conf/live/luckev.info/privkey.pem:/tmp/ssl/private/private.key:ro
cap_add:
- NET_ADMIN
- SYS_PTRACE
networks:
default:
external:
name: jenkins
The mailserver.env config file has this content:
#
# Mailserver Environment Variables
#
# 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
# critical => Only show critical messages
# error => Only show erroneous output
# **warn** => Show warnings
# info => Normal informational output
# debug => Also show debug messages
SUPERVISOR_LOGLEVEL=error
# 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=1
# empty => [email protected]
# => Specify the postmaster address
[email protected]
# Set different options for mynetworks option (can be overwrite in postfix-main.cf)
# **WARNING**: Adding the docker network's gateway to the list of trusted hosts, e.g. using the `network` or
# `connected-networks` option, can create an open relay
# https://github.com/docker-mailserver/docker-mailserver/issues/1405#issuecomment-590106498
# empty => localhost only
# host => Add docker host (ipv4 only)
# network => Add all docker containers (ipv4 only)
# connected-networks => Add all connected docker networks (ipv4 only)
PERMIT_DOCKER=host
# In case you network interface differs from 'eth0', e.g. when you are using HostNetworking in Kubernetes,
# you can set NETWORK_INTERFACE to whatever interface you want. This interface will then be used.
# - **empty** => eth0
NETWORK_INTERFACE=
# 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/docker-mailserver/docker-mailserver/wiki/)
TLS_LEVEL=
# Configures the handling of creating mails with forged sender addresses.
#
# empty => (not recommended, but default for backwards compatibility 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/docker-mailserver/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=manual
SSL_CERT_PATH=/tmp/ssl/cert/public.crt
SSL_KEY_PATH=/tmp/ssl/private/private.key
# 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 lmtp 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=
# Enables regular pflogsumm mail reports.
# This is a new option. The old REPORT options are still supported for backwards compatibility. If this is not set and reports are enabled with the old options, logrotate will be used.
#
# not set => No report
# daily_cron => Daily report for the previous day
# logrotate => Full report based on the mail log when it is rotated
PFLOGSUMM_TRIGGER=
# Recipient address for pflogsumm reports.
#
# not set => Use REPORT_RECIPIENT or POSTMASTER_ADDRESS
# => Specify the recipient address(es)
PFLOGSUMM_RECIPIENT=
# From address for pflogsumm reports.
#
# not set => Use REPORT_SENDER or POSTMASTER_ADDRESS
# => Specify the sender address
PFLOGSUMM_SENDER=
# Interval for logwatch report.
#
# none => No report is generated
# daily => Send a daily report
# weekly => Send a report every week
LOGWATCH_INTERVAL=weekly
# Recipient address for logwatch reports if they are enabled.
#
# not set => Use REPORT_RECIPIENT or POSTMASTER_ADDRESS
# => Specify the recipient address(es)
LOGWATCH_RECIPIENT=
# Enables a report being sent (created by pflogsumm) on a regular basis. (deprecated)
# **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 (deprecated)
# **empty** => mailserver-report@hostname
# => Specify the report sender (From) address
REPORT_SENDER=
# Changes the interval in which a report is being sent. (deprecated)
# **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
# Choose TCP/IP protocols to use
# **all** => All possible protocols.
# ipv4 => Use only IPv4 traffic. Most likely you want this behind Docker.
# ipv6 => Use only IPv6 traffic.
#
# Note: More details in http://www.postfix.org/postconf.5.html#inet_protocols
POSTFIX_INET_PROTOCOLS=all
#
# Spamassassin Section
#
ENABLE_SPAMASSASSIN=0
# deliver spam messages in the inbox (eventually tagged using SA_SPAM_SUBJECT)
SPAMASSASSIN_SPAM_TO_INBOX=1
# spam messages will be moved in the Junk folder (SPAMASSASSIN_SPAM_TO_INBOX=1 required)
MOVE_SPAM_TO_JUNK=1
# 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=1
# 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=
# e.g. `"(&(|(mail=*@%s)(mailalias=*@%s)(mailGroupMember=*@%s))(mailEnabled=TRUE))"`
# => Specify how ldap should be asked for domains
LDAP_QUERY_FILTER_DOMAIN=
#
# 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=
# Define the mailbox format to be used
# default is maildir, supported values are: sdbox, mdbox, maildir
DOVECOT_MAILBOX_FORMAT=maildir
# empty => no
# yes => Allow bind authentication for LDAP
# https://wiki.dovecot.org/AuthDatabase/LDAP/AuthBinds
DOVECOT_AUTH_BIND=
#
# 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
# whitelist host after N successful deliveries (N=0 to disable whitelisting)
POSTGREY_AUTO_WHITELIST_CLIENTS=5
#
# 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
# If yes you must/could specify SASLAUTHD_LDAP_TLS_CACERT_FILE or SASLAUTHD_LDAP_TLS_CACERT_DIR.
SASLAUTHD_LDAP_TLS_CHECK_PEER=
# File containing CA (Certificate Authority) certificate(s).
# empty => Nothing is added to the configuration
# Any value => Fills the `ldap_tls_cacert_file` option
SASLAUTHD_LDAP_TLS_CACERT_FILE=
# Path to directory with CA (Certificate Authority) certificates.
# empty => Nothing is added to the configuration
# Any value => Fills the `ldap_tls_cacert_dir` option
SASLAUTHD_LDAP_TLS_CACERT_DIR=
# Specify what password attribute to use for password verification.
# empty => Nothing is added to the configuration but the documentation says it is `userPassword` by default.
# Any value => Fills the `ldap_password_attr` option
SASLAUTHD_LDAP_PASSWORD_ATTR=
# empty => No sasl_passwd will be created
# string => `/etc/postfix/sasl_passwd` will be created with the string as password
SASL_PASSWD=
# empty => `bind` will be used as a default value
# `fastbind` => The fastbind method is used
# `custom` => The custom method uses userPassword attribute to verify the password
SASLAUTHD_LDAP_AUTH_METHOD=
# Specify the authentication mechanism for SASL bind
# empty => Nothing is added to the configuration
# Any value => Fills the `ldap_mech` option
SASLAUTHD_LDAP_MECH=
#
# SRS Section
#
# envelope_sender => Rewrite only envelope sender address (default)
# header_sender => Rewrite only header sender (not recommended)
# envelope_sender,header_sender => Rewrite both senders
# An email has an "envelope" sender (indicating the sending server) and a
# "header" sender (indicating who sent it). More strict SPF policies may require
# you to replace both instead of just the envelope sender.
SRS_SENDER_CLASSES=envelope_sender
# 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=
#
# Default Relay Host Section
#
# Setup relaying all mail through a default relay host
#
# empty => don't configure default relay host
# default host and optional port to relay all mail through
DEFAULT_RELAY_HOST=
#
# 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=
I would gladly appreciate any pointer in the right direction.
Hit me up, if you need more input for troubleshooting.
Sincerely,
Lucas
Subject
Incoming e-mails from external servers are not received.
Description
Hey there,
I recently installed your mailserver and it works pretty well.
The only problem I just cannot solve is the receival of incoming e-mails from external servers.
Intra-server mail transmission works fine though, so I think that the problem is somehow related to my DNS settings or maybe a misconfiguration of the mailserver (e.g. the hostname).
Listening on port 25 for inter-mailserver communication traffic results in this output directly after sending an e-mail from another e-mail domain to my mailserver domain.
However, no output is logged at the mailserver docker container and no e-mail is received.
After a few hours, an automatic mail with the following content is sent back to the sender e-mail address:
My DNS-Configuration (hosted by HostEurope) is the following:

The mailserver runs on a new server of Contabo with IPs
75.119.129.6and2a02:c206:3006:9356::1, hostnameluckev.infoand is supposed to serve mails formail.luckev.info.The docker-compose entry looks like this
The mailserver.env config file has this content:
I would gladly appreciate any pointer in the right direction.
Hit me up, if you need more input for troubleshooting.
Sincerely,
Lucas