Zimbra Collaboration Administrator Guide v8.8.11, December 2018 Table of Contents License. 2 Introduction. 3 Audience. 3 Third-Party Components . 3 Support and Contact Information . 3 Product Overview. 4 Architectural Overview . 4 Core Email, Calendar and Collaboration Functionality . 4 Zimbra Components . 5 Zimbra Application Packages . 6 Mail Flow — Multi-Server Configuration . 7 Zimbra System Directory Tree . 9 Zimbra Web Clients . 10 Web Services and Desktop Clients . 11 Offline Mode . 11 Security Measures . 11 Licensing. 14 License Types . 14 License Requirements. 14 License Usage by Account Type . 15 License Activation . 15 Obtain a License. 16 Managing Licenses . 16 Updating Your License . 18 Zimbra Mailbox Server . 19 Mailbox Server . 19 Web Application Server . 20 Web Application Server Split . 21 Backing Up the Mailbox Server . 21 Mailbox Server Logs . 22 IMAP . 23 Common IMAP Configuration settings . 23 Zimbra IMAPD Server. 24 IMAPD Configuration settings. 25 Zimbra Upstream IMAP Configuration. 26 IMAPD-related Configuration & Files . 26 Migrating to an imapd pool . 28 Multi-Node Configuration with Standalone IMAPD . 30 Zimbra LDAP Service. 32 LDAP Traffic Flow . 32 LDAP Directory Hierarchy . 32 Zimbra Collaboration LDAP Schema. 33 Account Authentication . 36 Global Address List . 39 Flushing LDAP Cache . 40 Zimbra Mail Transfer Agent . 43 Incoming Mail Routing Overview . 43 Zimbra MTA Deployment. 43 SMTP Authentication . 44 Anti-Virus and Anti-Spam Protection . 45 Receiving and Sending Mail . 60 Zimbra Proxy Server . ..