diff --git a/Dockerfile b/Dockerfile
index dd2a4e1..b579b07 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -10,11 +10,11 @@ ENV SMARTHOST=""
 ENV SMARTHOST_USER=""
 ENV SMARTHOST_PASS=""
 # ip addresses or networks to allow for relaying, separate multiple ones by semicolon
-ENV RELAYNETS=""
+ENV RELAYNETS="127.0.0.1/32"
 
-RUN apk add --no-cache exim bash
+RUN apk add --no-cache exim m4
 
-COPY exim.conf.tmpl /etc/exim
+COPY exim.conf.m4 /etc/exim
 COPY start.sh /etc/exim
 
 WORKDIR /etc/exim
@@ -22,6 +22,7 @@ WORKDIR /etc/exim
 EXPOSE 25
 
 CMD [ "./start.sh" ]
+#CMD [ "/usr/bin/m4 exim.conf.m4 > exim.conf && /usr/sbin/exim -bd -q15m -v" ]
 
  
 
diff --git a/ENV b/ENV
new file mode 100644
index 0000000..d7d2562
--- /dev/null
+++ b/ENV
@@ -0,0 +1,9 @@
+export HOSTNAME=`hostname`
+export LOCALMAILNAME="hottis.de"
+#export LOCALMAILNAME=""
+export SMARTHOST=smtprelaypool.ispgateway.de
+#export SMARTHOST=""
+export SMARTHOST_USER=pseudosmarthostuser@hottis.de 
+#export SMARTHOST_USER="_"
+export SMARTHOST_PASS="Chaediek3Chaer7u" 
+export RELAYNETS="0.0.0.0/0"
diff --git a/exim.conf.m4 b/exim.conf.m4
new file mode 100644
index 0000000..6bfa381
--- /dev/null
+++ b/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
+')
diff --git a/exim.conf.tmpl b/exim.conf.tmpl
deleted file mode 100644
index e655174..0000000
--- a/exim.conf.tmpl
+++ /dev/null
@@ -1,40 +0,0 @@
-primary_hostname = %HOSTNAME%
-qualify_domain = %LOCALMAILNAME%
-
-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
-  hosts_require_auth = *
-
-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"
-
-begin rewrite
-*@* ${1}@${qualify_domain} Ffrs
-
diff --git a/start.sh b/start.sh
index f4e671f..83f891a 100755
--- a/start.sh
+++ b/start.sh
@@ -1,15 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
-rm exim.conf
-
-cat exim.conf.tmpl \
-  | sed -e 's/%HOSTNAME%/'$HOSTNAME'/' \
-        -e 's#%RELAYNETS%#'$RELAYNETS'#' \
-        -e 's/%LOCALMAILNAME%/'$LOCALMAILNAME'/' \
-        -e 's/%SMARTHOST%/'$SMARTHOST'/' \
-        -e 's/%SMARTHOST_USER%/'$SMARTHOST_USER'/' \
-        -e 's/%SMARTHOST_PASS%/'$SMARTHOST_PASS'/' \
-  > exim.conf 
-
-exim -bd -q15m -v
+m4 exim.conf.m4 > exim.conf && exim -bd -q15m -v