SimpleLogin + mailcow setup

SimpleLogin

is also running in Docker containers, however Postfix has to be setup on the host due to lack of official Postfix image. I have been using it for some time.

Now, I’m trying to setup mailcow, and the instructions are straightforward and I have no problem setting mailcow up.

The problem is, I do not know how exactly to setup mailcow’s Postfix to relay emails to SimpleLogin.

My goal is:
abc.io - Personal Email domain, setup to use in mailcow
def.xyz - Alias domain, setup to use in SimpleLogin

According to SimpleLogin’s setup instructions, Postfix have to be setup with:
/etc/postfix/main.cf:

# POSTFIX config file, adapted for SimpleLogin
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
# fresh installs.
compatibility_level = 2

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtp_tls_security_level = may
smtpd_tls_security_level = may

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

alias_maps = hash:/etc/aliases
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 10.0.0.0/24

# Set your domain here
mydestination =
myhostname = app.mydomain.com
mydomain = mydomain.com
myorigin = mydomain.com

relay_domains = pgsql:/etc/postfix/pgsql-relay-domains.cf
transport_maps = pgsql:/etc/postfix/pgsql-transport-maps.cf

# HELO restrictions
smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_helo_restrictions =
    permit_mynetworks,
    reject_non_fqdn_helo_hostname,
    reject_invalid_helo_hostname,
    permit

# Sender restrictions:
smtpd_sender_restrictions =
    permit_mynetworks,
    reject_non_fqdn_sender,
    reject_unknown_sender_domain,
    permit

# Recipient restrictions:
smtpd_recipient_restrictions =
   reject_unauth_pipelining,
   reject_non_fqdn_recipient,
   reject_unknown_recipient_domain,
   permit_mynetworks,
   reject_unauth_destination,
   reject_rbl_client zen.spamhaus.org,
   reject_rbl_client bl.spamcop.net,
   permit

/etc/postfix/pgsql-relay-domains.cf:

# postgres config
hosts = localhost
user = myuser
password = mypassword
dbname = simplelogin

query = SELECT domain FROM custom_domain WHERE domain='%s' AND verified=true
    UNION SELECT '%s' WHERE '%s' = 'mydomain.com' LIMIT 1;

/etc/postfix/pgsql-transport-maps.cf:

# postgres config
hosts = localhost
user = myuser
password = mypassword
dbname = simplelogin

# forward to smtp:127.0.0.1:20381 for custom domain AND email domain
query = SELECT 'smtp:127.0.0.1:20381' FROM custom_domain WHERE domain = '%s' AND verified=true
    UNION SELECT 'smtp:127.0.0.1:20381' WHERE '%s' = 'mydomain.com' LIMIT 1;

Some keys are overlapping with mailcow’s default main.cf which I cannot simple add to data/conf/postfix/extra.cf.

Does anybody have any experiences setting them up? My progress is I have set up mailcow with abc.io, and SimpleLogin with def.xyz, but the missing part is the Postfix setup to relay mails to SimpleLogin. I have read this

, but I want to skip the Postfix on the host, and directly use mailcow’s Postfix to set up SimpleLogin.