diff --git a/lib/message-file.c b/lib/message-file.c
index 67828827..483ba1e9 100644
--- a/lib/message-file.c
+++ b/lib/message-file.c
@@ -117,7 +117,7 @@ notmuch_message_file_close (notmuch_message_file_t *message)
 }
 
 static notmuch_bool_t
-is_mbox (FILE *file)
+_is_mbox (FILE *file)
 {
     char from_buf[5];
     notmuch_bool_t ret = FALSE;
@@ -139,13 +139,12 @@ _notmuch_message_file_parse (notmuch_message_file_t *message)
     GMimeParser *parser;
     notmuch_status_t status = NOTMUCH_STATUS_SUCCESS;
     static int initialized = 0;
+    notmuch_bool_t is_mbox;
 
     if (message->message)
 	return NOTMUCH_STATUS_SUCCESS;
 
-    /* We no longer support mboxes at all. */
-    if (is_mbox (message->file))
-	return NOTMUCH_STATUS_FILE_NOT_EMAIL;
+    is_mbox = _is_mbox (message->file);
 
     if (! initialized) {
 	g_mime_init (GMIME_ENABLE_RFC2047_WORKAROUNDS);
@@ -163,7 +162,7 @@ _notmuch_message_file_parse (notmuch_message_file_t *message)
     g_mime_stream_file_set_owner (GMIME_STREAM_FILE (stream), FALSE);
 
     parser = g_mime_parser_new_with_stream (stream);
-    g_mime_parser_set_scan_from (parser, FALSE);
+    g_mime_parser_set_scan_from (parser, is_mbox);
 
     message->message = g_mime_parser_construct_message (parser);
     if (! message->message) {
@@ -171,6 +170,27 @@ _notmuch_message_file_parse (notmuch_message_file_t *message)
 	goto DONE;
     }
 
+    if (is_mbox) {
+	if (! g_mime_parser_eos (parser)) {
+	    /* This is a multi-message mbox. */
+	    status = NOTMUCH_STATUS_FILE_NOT_EMAIL;
+	    goto DONE;
+	}
+	/*
+	 * For historical reasons, we support single-message mboxes,
+	 * but this behavior is likely to change in the future, so
+	 * warn.
+	 */
+	static notmuch_bool_t mbox_warning = FALSE;
+	if (! mbox_warning) {
+	    mbox_warning = TRUE;
+	    fprintf (stderr, "\
+Warning: %s is an mbox containing a single message,\n\
+likely caused by misconfigured mail delivery.  Support for single-message\n\
+mboxes is deprecated and may be removed in the future.\n", message->filename);
+	}
+    }
+
   DONE:
     g_object_unref (stream);
     g_object_unref (parser);
diff --git a/test/T050-new.sh b/test/T050-new.sh
index 3c319542..ad46ee6d 100755
--- a/test/T050-new.sh
+++ b/test/T050-new.sh
@@ -163,6 +163,22 @@ rm -rf "${MAIL_DIR}"/two
 output=$(NOTMUCH_NEW)
 test_expect_equal "$output" "No new mail. Removed 3 messages."
 
+test_begin_subtest "Support single-message mbox (deprecated)"
+cat > "${MAIL_DIR}"/mbox_file1 <<EOF
+From test_suite@notmuchmail.org Fri Jan  5 15:43:57 2001
+From: Notmuch Test Suite <test_suite@notmuchmail.org>
+To: Notmuch Test Suite <test_suite@notmuchmail.org>
+Subject: Test mbox message 1
+
+Body.
+EOF
+output=$(NOTMUCH_NEW 2>&1)
+test_expect_equal "$output" \
+"Warning: ${MAIL_DIR}/mbox_file1 is an mbox containing a single message,
+likely caused by misconfigured mail delivery.  Support for single-message
+mboxes is deprecated and may be removed in the future.
+Added 1 new message to the database."
+
 # This test requires that notmuch new has been run at least once.
 test_begin_subtest "Skip and report non-mail files"
 generate_message
@@ -184,24 +200,14 @@ Subject: Test mbox message 2
 
 Body 2.
 EOF
-cat > "${MAIL_DIR}"/mbox_file1 <<EOF
-From test_suite@notmuchmail.org Fri Jan  5 15:43:57 2001
-From: Notmuch Test Suite <test_suite@notmuchmail.org>
-To: Notmuch Test Suite <test_suite@notmuchmail.org>
-Subject: Test mbox message 1
-
-Body.
-EOF
 output=$(NOTMUCH_NEW 2>&1)
 test_expect_equal "$output" \
 "Note: Ignoring non-mail file: ${MAIL_DIR}/.git/config
 Note: Ignoring non-mail file: ${MAIL_DIR}/.ignored_hidden_file
 Note: Ignoring non-mail file: ${MAIL_DIR}/ignored_file
 Note: Ignoring non-mail file: ${MAIL_DIR}/mbox_file
-Note: Ignoring non-mail file: ${MAIL_DIR}/mbox_file1
 Added 1 new message to the database."
 rm "${MAIL_DIR}"/mbox_file
-rm "${MAIL_DIR}"/mbox_file1
 
 test_begin_subtest "Ignore files and directories specified in new.ignore"
 generate_message
diff --git a/test/test-lib.sh b/test/test-lib.sh
index 8697d6a7..17deaaba 100644
--- a/test/test-lib.sh
+++ b/test/test-lib.sh
@@ -1081,15 +1081,14 @@ export NOTMUCH_CONFIG=$NOTMUCH_CONFIG
 
 # Here's what we are using here:
 #
-# --no-init-file	Don't load users ~/.emacs
-#
-# --no-site-file	Don't load the site-wide startup stuff
+# --quick              Use minimal customization. This implies --no-init-file,
+#		       --no-site-file and (emacs 24) --no-site-lisp
 #
 # --directory		Ensure that the local elisp sources are found
 #
 # --load		Force loading of notmuch.el and test-lib.el
 
-exec ${TEST_EMACS} --no-init-file --no-site-file \
+exec ${TEST_EMACS} --quick \
 	--directory "$TEST_DIRECTORY/../emacs" --load notmuch.el \
 	--directory "$TEST_DIRECTORY" --load test-lib.el \
 	"\$@"