diff --git a/ulib/debian b/ulib/debian
index cf66e9d..dcf86ff 100644
--- a/ulib/debian
+++ b/ulib/debian
@@ -122,9 +122,10 @@ function __network_backup() {
 
 function __network_hostname() {
     local hostname="${1%%.*}"
+    [ -f /etc/hostname ] || touch /etc/hostname
     if [ -n "$__DEBIAN_NETWORK_DEVEL_SHOW_MODIFS" ]; then
         uecho "Setting /etc/hostname to $hostname"
-    else
+    elif [ "$(</etc/hostname)" != "$hostname" ]; then
         __network_backup /etc/hostname
         echo "$hostname" >/etc/hostname
     fi
@@ -132,20 +133,22 @@ function __network_hostname() {
 
 function __network_mailname() {
     local host="$1"
+    [ -f /etc/mailname ] || touch /etc/mailname
     if [ -n "$__DEBIAN_NETWORK_DEVEL_SHOW_MODIFS" ]; then
         uecho "Setting /etc/mailname to $host"
-    else
+    elif [ "$(</etc/mailname)" != "$host" ]; then
         __network_backup /etc/mailname
         echo "$host" >/etc/mailname
     fi
 }
 
 function __network_fix_exim4() {
-    local host="$1"
+    local host="$1" oldhost="$2"
     local tmpfile; ac_set_tmpfile tmpfile
 
-    </etc/exim4/update-exim4.conf.conf sed '/^dc_other_hostnames=/c\
-'"dc_other_hostnames='$host'" >"$tmpfile"
+    sed </etc/exim4/update-exim4.conf.conf >"$tmpfile" "
+/^dc_other_hostnames=/c\\
+dc_other_hostnames='$host'"
     if [ -n "$__DEBIAN_NETWORK_DEVEL_SHOW_MODIFS" ]; then
         if testdiff "$tmpfile" /etc/exim4/update-exim4.conf.conf; then
             uecho "Setting /etc/exim4/update-exim4.conf.conf to:"
@@ -161,6 +164,33 @@ function __network_fix_exim4() {
     ac_clean "$tmpfile"
 }
 
+function __network_fix_postfix() {
+    local host="$1" oldhost="$2"
+    local tmpfile; ac_set_tmpfile tmpfile
+
+    awkrun </etc/postfix/main.cf >"$tmpfile" host="$host" oldhost="$oldhost" '
+/^myhostname *=/ { $0 = "myhostname = " host }
+/^mydestination *=/ {
+  gsub(" *" oldhost " *,? *", "")
+  if ($0 !~ (" *" host " *,? *")) {
+    sub(/^mydestination *= */, "mydestination = " host ", ")
+  }
+}
+{ print }'
+    if [ -n "$__DEBIAN_NETWORK_DEVEL_SHOW_MODIFS" ]; then
+        if testdiff "$tmpfile" /etc/postfix/main.cf; then
+            uecho "Setting /etc/postfix/main.cf to:"
+            cat "$tmpfile" | sed 's/^/    /g' 1>&2
+        else
+            uecho "/etc/postfix/main.cf: pas de modifications"
+        fi
+    elif testdiff "$tmpfile" /etc/postfix/main.cf; then
+        __network_backup /etc/postfix/main.cf
+        cat "$tmpfile" >/etc/postfix/main.cf
+    fi
+    ac_clean "$tmpfile"
+}
+
 function __network_hosts() {
     local host="$1" hostname="${1%%.*}" ip="$2"
     local shost="${host//./\\.}"
@@ -979,12 +1009,6 @@ iface lo inet loopback
         __network_hostname "$host"
         estep "/etc/mailname"
         __network_mailname "$host"
-        if [ -f "/etc/exim4/update-exim4.conf.conf" ]; then
-            estep "/etc/exim4/update-exim4.conf.conf"
-            __network_fix_exim4 "$host"
-        fi
-        # XXX tester la présence de postfix, et si nécessaire, modifier la
-        # configuration
         if [ -n "$mainip" ]; then
             estep "/etc/hosts"
             __network_hosts "$host" "$mainip"