Add configuration for exim4.

core/assets/exim/25_mm3_macros

@@ -0,0 +1,16 @@
+# Place this file at
+# /etc/exim4/conf.d/main/25_mm3_macros
+
+domainlist mm_domains=MY_DOMAIN_NAME
+
+MM3_LMTP_PORT=8024
+MM3_HOME=/opt/mailman/core/var
+
+
+################################################################
+# The configuration below is boilerplate:
+# you should not need to change it.
+
+# The path to the list receipt (used as the required file when
+# matching list addresses)
+MM3_LISTCHK=MM3_HOME/lists/${local_part}.${domain}

core/assets/exim/455_mm3_router

@@ -0,0 +1,15 @@
+# Place this file at
+# /etc/exim4/conf.d/router/455_mm3_router
+
+mailman3_router:
+  driver = accept
+  domains = +mm_domains
+  require_files = MM3_LISTCHK
+  local_part_suffix_optional
+  local_part_suffix = -admin : \
+     -bounces   : -bounces+* : \
+     -confirm   : -confirm+* : \
+     -join      : -leave     : \
+     -owner     : -request   : \
+     -subscribe : -unsubscribe
+  transport = mailman3_transport

core/assets/exim/55_mm3_transport

@@ -0,0 +1,11 @@
+# Place this file at
+# /etc/exim4/conf.d/router/55_mm3_transport
+
+mailman3_transport:
+  debug_print = "Email for mailman"
+  driver = smtp
+  protocol = lmtp
+  allow_localhost
+  hosts = 172.18.0.3
+  port = 8024
+  rcpt_include_affixes = true