Run SMTP on port 2525

Dockerfile

@@ -4,8 +4,10 @@ LABEL maintainer "Jonathan Gazeley"
 RUN apk add --no-cache postfix \
     && /usr/bin/newaliases
 
-COPY . /
+COPY smtp-relay.sh /
 
-EXPOSE 25
+COPY master.cf /etc/postfix/
+
+EXPOSE 2525
 
 ENTRYPOINT [ "/smtp-relay.sh" ]

master.cf

@@ -0,0 +1,64 @@
+#
+# Postfix master process configuration file.  For details on the format
+# of the file, see the master(5) manual page (command: "man 5 master" or
+# on-line: http://www.postfix.org/master.5.html).
+#
+# Do not forget to execute "postfix reload" after editing this file.
+#
+# ==========================================================================
+# service type  private unpriv  chroot  wakeup  maxproc command + args
+#               (yes)   (yes)   (no)    (never) (100)
+# ==========================================================================
+#smtp      inet  n       -       n       -       -       smtpd
+2525      inet  n       -       n       -       -       smtpd
+#smtp      inet  n       -       n       -       1       postscreen
+#smtpd     pass  -       -       n       -       -       smtpd
+#dnsblog   unix  -       -       n       -       0       dnsblog
+#tlsproxy  unix  -       -       n       -       0       tlsproxy
+# Choose one: enable submission for loopback clients only, or for any client.
+#127.0.0.1:submission inet n -   n       -       -       smtpd
+#submission inet n       -       n       -       -       smtpd
+#  -o syslog_name=postfix/submission
+#  -o smtpd_tls_security_level=encrypt
+#  -o smtpd_sasl_auth_enable=yes
+#  -o smtpd_tls_auth_only=yes
+#  -o local_header_rewrite_clients=static:all
+#  -o smtpd_reject_unlisted_recipient=no
+#     Instead of specifying complex smtpd_<xxx>_restrictions here,
+#     specify "smtpd_<xxx>_restrictions=$mua_<xxx>_restrictions"
+#     here, and specify mua_<xxx>_restrictions in main.cf (where
+#     "<xxx>" is "client", "helo", "sender", "relay", or "recipient").
+#  -o smtpd_client_restrictions=
+#  -o smtpd_helo_restrictions=
+#  -o smtpd_sender_restrictions=
+#  -o smtpd_relay_restrictions=
+#  -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
+#  -o milter_macro_daemon_name=ORIGINATING
+#628       inet  n       -       n       -       -       qmqpd
+pickup    unix  n       -       n       60      1       pickup
+cleanup   unix  n       -       n       -       0       cleanup
+qmgr      unix  n       -       n       300     1       qmgr
+#qmgr     unix  n       -       n       300     1       oqmgr
+tlsmgr    unix  -       -       n       1000?   1       tlsmgr
+rewrite   unix  -       -       n       -       -       trivial-rewrite
+bounce    unix  -       -       n       -       0       bounce
+defer     unix  -       -       n       -       0       bounce
+trace     unix  -       -       n       -       0       bounce
+verify    unix  -       -       n       -       1       verify
+flush     unix  n       -       n       1000?   0       flush
+proxymap  unix  -       -       n       -       -       proxymap
+proxywrite unix -       -       n       -       1       proxymap
+smtp      unix  -       -       n       -       -       smtp
+relay     unix  -       -       n       -       -       smtp
+        -o syslog_name=postfix/$service_name
+#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
+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
+postlog   unix-dgram n  -       n       -       1       postlogd