Release 1.6.19 of the Google Apps Directory Sync tool is now available for download. It now includes support for alias exclusion. If you have Google Apps users who should not be deleted, moved or modified during synchronization, you can specify those users as match rules on alias email address. Match rules include exact match, regular expressions based match and substring match. To start using it, set up user alias rules in the Google Apps Directory Sync Configuration Manager, in the section for Google Apps Exclusion Rules.