Initial commit

Dockerfile

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+FROM debian:stretch-slim
+MAINTAINER Bytemark Hosting "support@bytemark.co.uk"
+
+# Install exim4
+ENV DEBIAN_FRONTEND noninteractive
+RUN set -ex; \
+    apt-get update; \
+    apt-get install -y exim4-daemon-light; \
+    apt-get clean
+
+# Copy the main script.
+COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
+
+# We expose exim on port 25.
+EXPOSE 25/tcp
+
+ENTRYPOINT [ "docker-entrypoint.sh" ]
+CMD [ "exim", "-bdf", "-v", "-q30m" ]

README.md

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+# https://github.com/BytemarkHosting/docker-smtp
+
+## Maintained by: [Bytemark Hosting](https://www.bytemark.co.uk)
+
+This is the Git repo of the bytemark/smtp image.
+
+This image allows linked containers to send outgoing email. You can configure
+it to send email directly to the recipient, or to act as a smart host and relay
+mail to an intermediate server (eg, GMail, SendGrid).
+
+## Usage
+
+In the following examples, linked containers would be able to connect via SMTP
+to hostname `mail` and port `25` to send outoing email.
+
+### Basic SMTP server
+
+In this example, linked containers can connect to hostname `mail` and port `25`
+to send outgoing email. The SMTP container sends email out directly.
+
+```
+docker run --restart always --name mail -d bytemark/smtp
+```
+
+Via Docker Compose:
+
+```
+  mail:
+    image: bytemark/smtp
+    restart: always
+```
+
+Optionally, set `MAILNAME` environment variable. (By default, Exim will use the
+hostname of the container.)
+
+### SMTP smart host
+
+In this example, linked containers can connect to hostname `mail` and port `25`
+to send outgoing email. The SMTP container acts as a smart host and relays mail
+to an intermediate server server (eg, GMail, SendGrid).
+
+```
+docker run --restart always --name mail -d bytemark/smtp \
+    -e RELAY_HOST=smtp.example.com \
+    -e RELAY_PORT=587 \
+    -e RELAY_USERNAME=alice@example.com \
+    -e RELAY_PASSWORD=secretpassword
+```
+
+Via Docker Compose:
+
+```
+  mail:
+    image: bytemark/smtp
+    restart: always
+    environment:
+      RELAY_HOST: smtp.example.com
+      RELAY_PORT: 587
+      RELAY_USERNAME: alice@example.com
+      RELAY_PASSWORD: secretpassword
+```
+
+Optionally, set `MAILNAME` environment variable. (By default, Exim will use the
+hostname of the container.)

docker-entrypoint.sh

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+#!/bin/sh
+set -e
+CONFDIR=/etc/exim4
+
+# Set smarthost.
+DC_EXIMCONFIG_CONFIGTYPE="internet"
+if [ "x$RELAY_HOST" != "x" ]; then
+    DC_EXIMCONFIG_CONFIGTYPE="satellite"
+    DC_SMARTHOST="$RELAY_HOST::${RELAY_PORT:-25}"
+    if [ "x$RELAY_USERNAME" != "x" ] && [ "x$RELAY_PASSWORD" != "x" ]; then
+        printf '%s\n' "*:$RELAY_USERNAME:$RELAY_PASSWORD" > "$CONFDIR/passwd.client"
+    fi
+fi
+
+# Write exim configuration.
+cat << EOF > "$CONFDIR/update-exim4.conf.conf"
+dc_eximconfig_configtype='$DC_EXIMCONFIG_CONFIGTYPE'
+dc_other_hostnames=''
+dc_local_interfaces='0.0.0.0'
+dc_readhost=''
+dc_relay_domains='*'
+dc_minimaldns='false'
+dc_relay_nets='0.0.0.0/0'
+dc_smarthost='${DC_SMARTHOST:-}'
+CFILEMODE='644'
+dc_use_split_config='false'
+dc_hide_mailname='true'
+dc_mailname_in_oh='true'
+dc_localdelivery='mail_spool'
+EOF
+
+# Set primary_hostname.
+if [ "x$MAILNAME" != "x" ]; then
+    printf '%s\n' "$MAILNAME" > /etc/mailname
+    printf '%s\n' "MAIN_HARDCODE_PRIMARY_HOSTNAME=$MAILNAME" >> "$CONFDIR/update-exim4.conf.conf"
+fi
+
+# Apply exim configuration.
+update-exim4.conf
+
+exec "$@"