diff --git a/network/postfix/postfix.SlackBuild b/network/postfix/postfix.SlackBuild
index 579713482b..fa50f30a77 100644
--- a/network/postfix/postfix.SlackBuild
+++ b/network/postfix/postfix.SlackBuild
@@ -21,10 +21,19 @@
 
 PRGNAM="postfix"
 VERSION="2.6.1"
-ARCH=${ARCH:-i486}
 BUILD=${BUILD:-1}
 TAG=${TAG:-_SBo}
 
+# Automatically determine the architecture we're building on:
+if [ -z "$ARCH" ]; then
+  case "$( uname -m )" in
+    i?86) ARCH=i486 ;;
+    arm*) ARCH=arm ;;
+    # Unless $ARCH is already set, use uname -m for all other archs:
+       *) ARCH=$( uname -m ) ;;
+  esac
+fi
+
 CWD=$(pwd)
 TMP=${TMP:-/tmp/SBo}
 PKG="$TMP/package-$PRGNAM"
@@ -39,6 +48,9 @@ elif [ "$ARCH" = "i686" ]; then
 elif [ "$ARCH" = "x86_64" ]; then
   SLKCFLAGS="-O2 -fPIC"
   LIBDIRSUFFIX="64"
+else
+  SLKCFLAGS="-O2"
+  LIBDIRSUFFIX=""
 fi
 
 set -e