diff -r 8b358effa78b -r 4cf0161c445a configure.ac
--- a/configure.ac	Mon Mar 14 11:20:05 2011 +0100
+++ b/configure.ac	Mon Mar 14 16:57:47 2011 +0100
@@ -513,6 +513,31 @@
 fi
 
 #------------------------------------------------------------------------------
+# Use 2 datagrams (payload+last-byte) when sending to mailbox (reduces frame size)
+#------------------------------------------------------------------------------
+
+AC_ARG_ENABLE([mboxframesize],
+    AS_HELP_STRING([--enable-mboxframesize],
+                   [Reduced frame size when sending to mailbox, uses 2 datagrams (default: no)]),
+    [
+        case "${enableval}" in
+            yes) mboxframesize=1
+                ;;
+            no) mboxframesize=0
+                ;;
+            *) AC_MSG_ERROR([Invalid value for --enable-mboxframesize])
+                ;;
+        esac
+    ],
+    [mboxframesize=0]
+)
+
+if test "x${mboxframesize}" = "x1"; then
+    AC_DEFINE([EC_REDUCE_MBOXFRAMESIZE], [1], [Reduced frame size when sending to mailbox])
+fi
+
+
+#------------------------------------------------------------------------------
 # Read alias address from register
 #------------------------------------------------------------------------------