Oh Jesus Christ this is embarrassing…
First of all, I am definitely on the right server
(proxmox, dedicated virtual machine only for this ), BUT
the docker version of mailcow actually doesn’t use the configuration you would expect under /etc/postfix ( because that’s where I looked and configured ), but in a different location and that’s going to …/data/conf/postfix/… into the filesystem of the Docker server ( volume ) and here I guess you have to make changes if you want to.
Even if you laugh now 
have to say in my defense that I never had to set anything outside the GUI with Mailcow, still a bit embarrassing…
thanks for your link and doing my research job…
Looking at the file now I see the following.
main.cf
# --------------------------------------------------------------------------
# Please create a file "extra.cf" for persistent overrides to main.cf
# --------------------------------------------------------------------------
biff = no
append_dot_mydomain = no
smtpd_tls_cert_file = /etc/ssl/mail/cert.pem
smtpd_tls_key_file = /etc/ssl/mail/key.pem
tls_server_sni_maps = hash:/opt/postfix/conf/sni.map
smtpd_tls_received_header = yes
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_relay_restrictions = permit_mynetworks,
permit_sasl_authenticated,
defer_unauth_destination
# alias maps are auto-generated in postfix.sh on startup
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
relayhost =
mynetworks_style = subnet
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
bounce_queue_lifetime = 1d
broken_sasl_auth_clients = yes
disable_vrfy_command = yes
maximal_backoff_time = 1800s
maximal_queue_lifetime = 5d
delay_warning_time = 4h
message_size_limit = 104857600
milter_default_action = tempfail
milter_protocol = 6
minimal_backoff_time = 300s
plaintext_reject_code = 550
postscreen_access_list = permit_mynetworks,
cidr:/opt/postfix/conf/custom_postscreen_whitelist.cidr,
cidr:/opt/postfix/conf/postscreen_access.cidr,
tcp:127.0.0.1:10027
postscreen_bare_newline_enable = no
postscreen_blacklist_action = drop
postscreen_cache_cleanup_interval = 24h
postscreen_cache_map = proxy:btree:$data_directory/postscreen_cache
postscreen_dnsbl_action = enforce
postscreen_dnsbl_sites = wl.mailspike.net=127.0.0.[18;19;20]*-2
hostkarma.junkemailfilter.com=127.0.0.1*-2
list.dnswl.org=127.0.[0..255].0*-2
list.dnswl.org=127.0.[0..255].1*-4
list.dnswl.org=127.0.[0..255].2*-6
list.dnswl.org=127.0.[0..255].3*-8
ix.dnsbl.manitu.net*2
bl.spamcop.net*2
bl.suomispam.net*2
hostkarma.junkemailfilter.com=127.0.0.2*3
hostkarma.junkemailfilter.com=127.0.0.4*2
hostkarma.junkemailfilter.com=127.0.1.2*1
backscatter.spameatingmonkey.net*2
bl.ipv6.spameatingmonkey.net*2
bl.spameatingmonkey.net*2
b.barracudacentral.org=127.0.0.2*7
bl.mailspike.net=127.0.0.2*5
bl.mailspike.net=127.0.0.[10;11;12]*4
dnsbl.sorbs.net=127.0.0.10*8
dnsbl.sorbs.net=127.0.0.5*6
dnsbl.sorbs.net=127.0.0.7*3
dnsbl.sorbs.net=127.0.0.8*2
dnsbl.sorbs.net=127.0.0.6*2
dnsbl.sorbs.net=127.0.0.9*2
zen.spamhaus.org=127.0.0.[10;11]*8
zen.spamhaus.org=127.0.0.[4..7]*6
zen.spamhaus.org=127.0.0.3*4
zen.spamhaus.org=127.0.0.2*3
postscreen_dnsbl_threshold = 6
postscreen_dnsbl_ttl = 5m
postscreen_greet_action = enforce
postscreen_greet_banner = $smtpd_banner
postscreen_greet_ttl = 2d
postscreen_greet_wait = 3s
postscreen_non_smtp_command_enable = no
postscreen_pipelining_enable = no
proxy_read_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_sasl_passwd_maps_transport_maps.cf,
proxy:mysql:/opt/postfix/conf/sql/mysql_mbr_access_maps.cf,
proxy:mysql:/opt/postfix/conf/sql/mysql_tls_enforce_in_policy.cf,
$sender_dependent_default_transport_maps,
$smtp_tls_policy_maps,
$local_recipient_maps,
$mydestination,
$virtual_alias_maps,
$virtual_alias_domains,
$virtual_mailbox_maps,
$virtual_mailbox_domains,
$relay_recipient_maps,
$relay_domains,
$canonical_maps,
$sender_canonical_maps,
$sender_bcc_maps,
$recipient_bcc_maps,
$recipient_canonical_maps,
$relocated_maps,
$transport_maps,
$mynetworks,
$smtpd_sender_login_maps,
$smtp_sasl_password_maps
queue_run_delay = 300s
relay_domains = proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_relay_domain_maps.cf
relay_recipient_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_relay_recipient_maps.cf
sender_dependent_default_transport_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_sender_dependent_default_transport_maps.cf
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
smtp_tls_cert_file = /etc/ssl/mail/cert.pem
smtp_tls_key_file = /etc/ssl/mail/key.pem
smtp_tls_loglevel = 1
smtp_dns_support_level = dnssec
smtp_tls_security_level = dane
smtpd_data_restrictions = reject_unauth_pipelining, permit
smtpd_delay_reject = yes
smtpd_error_sleep_time = 10s
smtpd_hard_error_limit = ${stress?1}${stress:5}
smtpd_helo_required = yes
smtpd_proxy_timeout = 600s
smtpd_recipient_restrictions = check_recipient_mx_access proxy:mysql:/opt/postfix/conf/sql/mysql_mbr_access_maps.cf,
permit_sasl_authenticated,
permit_mynetworks,
check_recipient_access proxy:mysql:/opt/postfix/conf/sql/mysql_tls_enforce_in_policy.cf,
reject_invalid_helo_hostname,
reject_unauth_destination
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_path = inet:dovecot:10001
smtpd_sasl_type = dovecot
smtpd_sender_login_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_sender_acl.cf
smtpd_sender_restrictions = reject_authenticated_sender_login_mismatch,
permit_mynetworks,
permit_sasl_authenticated,
reject_unlisted_sender,
reject_unknown_sender_domain
smtpd_soft_error_limit = 3
smtpd_tls_auth_only = yes
smtpd_tls_dh1024_param_file = /etc/ssl/mail/dhparams.pem
smtpd_tls_eecdh_grade = auto
smtpd_tls_exclude_ciphers = ECDHE-RSA-RC4-SHA, RC4, aNULL, DES-CBC3-SHA, ECDHE-RSA-DES-CBC3-SHA, EDH-RSA-DES-CBC3-SHA
smtpd_tls_loglevel = 1
# Mandatory protocols and ciphers are used when a connections is enforced to use TLS
# Does _not_ apply to enforced incoming TLS settings per mailbox
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
lmtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtpd_tls_mandatory_ciphers = high
smtp_tls_protocols = !SSLv2, !SSLv3
lmtp_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtpd_tls_protocols = !SSLv2, !SSLv3
smtpd_tls_security_level = may
tls_preempt_cipherlist = yes
tls_ssl_options = NO_COMPRESSION, NO_RENEGOTIATION
virtual_alias_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_alias_maps.cf,
proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_resource_maps.cf,
proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_spamalias_maps.cf,
proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_alias_domain_maps.cf
virtual_gid_maps = static:5000
virtual_mailbox_base = /var/vmail/
virtual_mailbox_domains = proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_domains_maps.cf
# -- moved to rspamd on 2021-06-01
#recipient_bcc_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_recipient_bcc_maps.cf
#sender_bcc_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_sender_bcc_maps.cf
recipient_canonical_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_recipient_canonical_maps.cf
recipient_canonical_classes = envelope_recipient
virtual_mailbox_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_virtual_mailbox_maps.cf
virtual_minimum_uid = 104
virtual_transport = lmtp:inet:dovecot:24
virtual_uid_maps = static:5000
smtpd_milters = inet:rspamd:9900
non_smtpd_milters = inet:rspamd:9900
milter_mail_macros = i {mail_addr} {client_addr} {client_name} {auth_authen}
mydestination = localhost.localdomain, localhost
smtp_address_preference = any
smtp_sender_dependent_authentication = yes
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_sasl_passwd_maps_sender_dependent.cf
smtp_sasl_security_options =
smtp_sasl_mechanism_filter = plain, login
smtp_tls_policy_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_tls_policy_override_maps.cf
smtp_header_checks = pcre:/opt/postfix/conf/anonymize_headers.pcre
mail_name = Postcow
# local_transport map catches local destinations and prevents routing local dests when the next map would route "*"
# Use custom_transport.pcre for custom transports
transport_maps = pcre:/opt/postfix/conf/custom_transport.pcre,
pcre:/opt/postfix/conf/local_transport,
proxy:mysql:/opt/postfix/conf/sql/mysql_relay_ne.cf,
proxy:mysql:/opt/postfix/conf/sql/mysql_transport_maps.cf
smtp_sasl_auth_soft_bounce = no
postscreen_discard_ehlo_keywords = silent-discard, dsn
compatibility_level = 2
smtputf8_enable = no
# Define protocols for SMTPS and submission service
submission_smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtps_smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
parent_domain_matches_subdomains = debug_peer_list,fast_flush_domains,mynetworks,qmqpd_authorized_clients
# DO NOT EDIT ANYTHING BELOW #
# User overrides #
myhostname = mail.unixuser.de
smtp_tls_protocols = !SSLv2, !SSLv3,!TLSv1,!TLSv1.1
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_protocols = !SSLv2, !SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3,!TLSv1,!TLSv1.1
lmtp_tls_protocols = !SSLv2, !SSLv3,!TLSv1,!TLSv1.1
lmtp_tls_mandatory_protocols = !SSLv2, !SSLv3,!TLSv1,!TLSv1.1
# SSL/TLS supported ciphers
smtp_tls_ciphers = high
smtp_tls_mandatory_ciphers = high
smtpd_tls_ciphers = high
smtpd_tls_mandatory_ciphers = high
tls_high_cipherlist = tls_high_cipherlist = ECDHE-ECDSA-AES256-GCM-SHA384:TLS_AES_256_GCM_SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:TLS_CHACHA20_POLY1305_SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:TLS_AES_128_GCM_SHA256:ECDHE-RSA-AES256-GCM-SHA384:TLS_AES_256_GCM_SHA384:ECDHE-RSA-CHACHA20-POLY1305:TLS_CHACHA20_POLY1305_SHA256:ECDHE-RSA-AES128-GCM-SHA256:TLS_AES_128_GCM_SHA256
smtpd_tls_eecdh_grade = ultra
master.cf
# inter-mx with postscreen on 25/tcp
smtp inet n - n - 1 postscreen
10025 inet n - n - 1 postscreen
-o postscreen_upstream_proxy_protocol=haproxy
-o syslog_name=haproxy
smtpd pass - - n - - smtpd
-o smtpd_helo_restrictions=permit_mynetworks,reject_non_fqdn_helo_hostname
-o smtpd_sasl_auth_enable=no
-o smtpd_sender_restrictions=permit_mynetworks,reject_unlisted_sender,reject_unknown_sender_domain
# smtpd tls-wrapped (smtps) on 465/tcp
# TLS protocol can be modified by setting smtps_smtpd_tls_mandatory_protocols in extra.cf
smtps inet n - n - - smtpd
-o smtpd_tls_wrappermode=yes
-o smtpd_client_restrictions=permit_mynetworks,permit_sasl_authenticated,reject
-o smtpd_tls_mandatory_protocols=$smtps_smtpd_tls_mandatory_protocols
-o tls_preempt_cipherlist=yes
-o cleanup_service_name=smtp_sender_cleanup
-o syslog_name=postfix/smtps
10465 inet n - n - - smtpd
-o smtpd_upstream_proxy_protocol=haproxy
-o smtpd_tls_wrappermode=yes
-o smtpd_client_restrictions=permit_mynetworks,permit_sasl_authenticated,reject
-o smtpd_tls_mandatory_protocols=$smtps_smtpd_tls_mandatory_protocols
-o tls_preempt_cipherlist=yes
-o cleanup_service_name=smtp_sender_cleanup
-o syslog_name=postfix/smtps-haproxy
# smtpd with starttls on 587/tcp
# TLS protocol can be modified by setting submission_smtpd_tls_mandatory_protocols in extra.cf
submission inet n - n - - smtpd
-o smtpd_client_restrictions=permit_mynetworks,permit_sasl_authenticated,reject
-o smtpd_enforce_tls=yes
-o smtpd_tls_security_level=encrypt
-o smtpd_tls_mandatory_protocols=$submission_smtpd_tls_mandatory_protocols
-o tls_preempt_cipherlist=yes
-o cleanup_service_name=smtp_sender_cleanup
-o syslog_name=postfix/submission
10587 inet n - n - - smtpd
-o smtpd_upstream_proxy_protocol=haproxy
-o smtpd_client_restrictions=permit_mynetworks,permit_sasl_authenticated,reject
-o smtpd_enforce_tls=yes
-o smtpd_tls_security_level=encrypt
-o smtpd_tls_mandatory_protocols=$submission_smtpd_tls_mandatory_protocols
-o tls_preempt_cipherlist=yes
-o cleanup_service_name=smtp_sender_cleanup
-o syslog_name=postfix/submission-haproxy
# used by SOGo
# smtpd_sender_restrictions should match main.cf, but with check_sasl_access prepended for login-as-mailbox-user function
588 inet n - n - - smtpd
-o smtpd_client_restrictions=permit_mynetworks,permit_sasl_authenticated,reject
-o smtpd_tls_auth_only=no
-o smtpd_sender_restrictions=check_sasl_access,regexp:/opt/postfix/conf/allow_mailcow_local.regexp,reject_authenticated_sender_login_mismatch,permit_mynetworks,permit_sasl_authenticated,reject_unlisted_sender,reject_unknown_sender_domain
-o cleanup_service_name=smtp_sender_cleanup
-o syslog_name=postfix/sogo
# used to reinject quarantine mails
590 inet n - n - - smtpd
-o smtpd_helo_restrictions=
-o smtpd_client_restrictions=permit_mynetworks,reject
-o smtpd_tls_auth_only=no
-o smtpd_milters=
-o non_smtpd_milters=
-o syslog_name=postfix/quarantine
# used to send bcc mails
591 inet n - n - - smtpd
-o smtpd_helo_restrictions=
-o smtpd_client_restrictions=permit_mynetworks,reject
-o smtpd_tls_auth_only=no
-o smtpd_milters=
-o non_smtpd_milters=
-o syslog_name=postfix/bcc
# enforced smtp connector
smtp_enforced_tls unix - - n - - smtp
-o smtp_tls_security_level=encrypt
-o syslog_name=enforced-tls-smtp
-o smtp_delivery_status_filter=pcre:/opt/postfix/conf/smtp_dsn_filter
# smtp connector used, when a transport map matched
# this helps to have different sasl maps than we have with sender dependent transport maps
smtp_via_transport_maps unix - - n - - smtp
-o smtp_sasl_password_maps=proxy:mysql:/opt/postfix/conf/sql/mysql_sasl_passwd_maps_transport_maps.cf
tlsproxy unix - - n - 0 tlsproxy
dnsblog unix - - n - 0 dnsblog
pickup fifo n - n 60 1 pickup
cleanup unix n - n - 0 cleanup
qmgr fifo n - n 300 1 qmgr
tlsmgr unix - - n 1000? 1 tlsmgr
rewrite unix - - n - - trivial-rewrite
bounce unix - - n - 0 bounce
defer unix - - n - 0 bounce
trace unix - - n - 0 bounce
verify unix - - n - 1 verify
flush unix n - n 1000? 0 flush
proxymap unix - - n - - proxymap
proxywrite unix - - n - 1 proxymap
smtp unix - - n - - smtp
relay unix - - n - - smtp
showq unix n - n - - showq
error unix - - n - - error
retry unix - - n - - error
discard unix - - n - - discard
local unix - n n - - local
virtual unix - n n - - virtual
lmtp unix - - n - - lmtp
anvil unix - - n - 1 anvil
scache unix - - n - 1 scache
maildrop unix - n n - - pipe flags=DRhu
user=vmail argv=/usr/bin/maildrop -d ${recipient}
# used to anonymize sender IP
smtp_sender_cleanup unix n - y - 0 cleanup
-o header_checks=$smtp_header_checks
# start whitelist_fwd
127.0.0.1:10027 inet n n n - 0 spawn user=nobody argv=/usr/local/bin/whitelist_forwardinghosts.sh
# end whitelist_fwd
# start watchdog-specific
# logs to local7 (hidden)
589 inet n - n - - smtpd
-o smtpd_client_restrictions=permit_mynetworks,reject
-o syslog_name=watchdog
-o syslog_facility=local7
-o smtpd_milters=
-o cleanup_service_name=watchdog_cleanup
-o non_smtpd_milters=
watchdog_cleanup unix n - n - 0 cleanup
-o syslog_name=watchdog
-o syslog_facility=local7
-o queue_service_name=watchdog_qmgr
watchdog_qmgr fifo n - n 300 1 qmgr
-o syslog_facility=local7
-o syslog_name=watchdog
-o rewrite_service_name=watchdog_rewrite
watchdog_rewrite unix - - n - - trivial-rewrite
-o syslog_facility=local7
-o syslog_name=watchdog
-o local_transport=watchdog_discard
watchdog_discard unix - - n - - discard
-o syslog_facility=local7
-o syslog_name=watchdog
# end watchdog-specific
Of course, this explains why simply nothing changed after changing the configuration.
Phew…hopefully not too many people read this :=)
