alpine approach

Dockerfile

@@ -1,4 +1,4 @@
-FROM debian:bookworm
+FROM alpine:3.21.0
 
 LABEL Maintainer="Wolfgang Hottgenroth <woho@hottis.de>"
 LABEL ImageName=""
@@ -7,27 +7,15 @@ LABEL ImageName=""
 ENV LOCALMAILNAME=""
 # smarthost to send mail to
 ENV SMARTHOST=""
-# recipient addresses for root aliases, separate multiple addresses by space
-ENV ROOT=""
 # ip addresses or networks to allow for relaying, separate multiple ones by semicolon
 ENV RELAYNETS=""
 
-RUN \
+RUN apk add --no-cache exim bash
-  apt update && \
-  apt upgrade -y --autoremove && \
-  apt install -y exim4-daemon-light ca-certificates curl && \ 
-  rm -rf /var/lib/apt/lists/*
 
-COPY update-exim4.conf.tmpl /etc/exim4/
+WORKDIR /etc/exim
-COPY aliases.tmpl /etc/exim4/
-COPY adjust-config.sh /etc/exim4/
-COPY start.sh /etc/exim4/
-
-WORKDIR /etc/exim4
 
 EXPOSE 25
 
-CMD [ "./start.sh" ]
 
  
 

aliases.tmpl

@@ -1,14 +0,0 @@
-mailer-daemon: postmaster
-postmaster: root
-nobody: root
-hostmaster: root
-usenet: root
-news: root
-webmaster: root
-www: root
-ftp: root
-abuse: root
-noc: root
-security: root
-root: %ROOT%
-

exim.conf

@@ -0,0 +1,28 @@
+primary_hostname = mail.hottis.de
+qualify_domain = hottis.de
+
+acl_smtp_rcpt = acl_check_rcpt
+
+begin routers
+smarthost_route:
+  driver = manualroute
+  domains = *
+  transport = smarthost_smtp
+  route_list = * mail.bighost.com
+
+begin transports
+smarthost_smtp:
+  driver = smtp
+  port = 25
+  multi_domain
+
+begin acl
+acl_check_rcpt:
+  accept
+    hosts = 172.17.0.0/16 : 172.16.3.0/24
+  deny
+    message = "Relaying denied"
+
+begin rewrite
+*@* ${expand:${1}@${qualify_domain}}
+

update-exim4.conf.tmpl

@@ -1,14 +0,0 @@
-dc_eximconfig_configtype='satellite'
-dc_other_hostnames='%HOSTNAME%'
-dc_local_interfaces='0.0.0.0'
-dc_readhost='%LOCALMAILNAME%'
-dc_relay_domains=''
-dc_minimaldns='false'
-dc_relay_nets='%RELAYNETS%'
-dc_smarthost='%SMARTHOST%'
-CFILEMODE='644'
-dc_use_split_config='false'
-dc_hide_mailname='true'
-dc_mailname_in_oh='true'
-dc_localdelivery='mail_spool'
-