use m4 for config generation

exim.conf.m4

@@ -0,0 +1,64 @@
+dnl values
+define(`HOSTNAME', esyscmd(`echo -n $HOSTNAME'))dnl
+define(`LOCALMAILNAME', esyscmd(`echo -n $LOCALMAILNAME'))dnl
+define(`SMARTHOST', esyscmd(`echo -n $SMARTHOST'))dnl
+define(`SMARTHOST_USER', esyscmd(`echo -n $SMARTHOST_USER'))dnl
+define(`SMARTHOST_PASS', esyscmd(`echo -n $SMARTHOST_PASS'))dnl
+define(`RELAYNETS', esyscmd(`echo -n $RELAYNETS'))dnl
+
+ifelse(SMARTHOST, `', `
+errprint(`Error: SMARTHOST not set')
+m4exit(1)
+')
+
+ifelse(HOSTNAME, `', `
+errprint(`Error: HOSTNAME not set')
+m4exit(1)
+')
+
+dnl template for exim.conf
+
+primary_hostname = HOSTNAME
+
+acl_smtp_rcpt = acl_check_rcpt
+
+begin routers
+smarthost_route:
+  driver = manualroute
+  domains = *
+  transport = smarthost_smtp
+  route_list = * SMARTHOST
+
+begin transports
+smarthost_smtp:
+  driver = smtp
+  port = 25
+  multi_domain
+ifelse(SMARTHOST_USER, `', `', `dnl
+  hosts_require_auth = *
+')
+
+ifelse(SMARTHOST_USER, `', `', `
+begin authenticators
+plain:
+  driver = plaintext
+  public_name = PLAIN
+  client_send = ^SMARTHOST_USER^SMARTHOST_PASS
+
+login:
+  driver = plaintext
+  public_name = LOGIN
+  client_send = : SMARTHOST_USER : SMARTHOST_PASS
+')
+
+begin acl
+acl_check_rcpt:
+  accept
+    hosts = RELAYNETS
+  deny
+    message = "Relaying denied"
+
+ifelse(LOCALMAILNAME, `', `', `
+begin rewrite
+*@* ${1}@LOCALMAILNAME Ffrs
+')