new file mode 100644
--- /dev/null
+++ b/db/moz.configure
@@ -0,0 +1,8 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+imply_option('--enable-dbm', True,
+             reason="dbm is required for building Thunderbird and SeaMonkey.")

--- a/mailnews/moz.configure
+++ b/mailnews/moz.configure
@@ -46,8 +46,10 @@ option('--disable-mapi',
 @depends_if('--enable-mapi',
             when=target_is_windows)
 def mapi_support(arg):
     return True
 
 
 set_config('MOZ_MAPI_SUPPORT', mapi_support)
 set_define('MOZ_MAPI_SUPPORT', mapi_support)
+
+include('../db/moz.configure')