Zimbra Collaboration Administrator Guide June 2019 Version Zimbra Network Edition V 8.8.15, revised 2021-04-21 Table of Contents License. 2 Introduction. 3 Audience. 3 Third-Party Components . 3 Support and Contact Information . 3 Product Life Cycle. 4 Component Deprecation Statements. 4 Product Overview. 5 Architectural Overview . 5 Core Email, Calendar and Collaboration Functionality . 5 Zimbra Components . 6 Zimbra Application Packages . 7 Mail Flow — Multi-Server Configuration . 8 Zimbra System Directory Tree . 10 Zimbra Web Clients . 11 Web Services and Desktop Clients . 11 Offline Mode . 12 Security Measures . 12 Licensing. 15 License Types . 15 Zimbra License Requirements . 15 License Usage by Account Type . 16 License Activation . 16 Obtain a License. 18 Managing Licenses . 18 Updating Your License . 19 License Reconciliation and Data Collection Notice . 20 Zimbra Mailbox Server . 21 Mailbox Server . 21 Web Application Server . 22 Web Application Server Split . 23 Backing Up the Mailbox Server . 23 Mailbox Server Logs . 24 IMAP . 25 Common IMAP Configuration settings . 25 Zimbra LDAP Service. 27 LDAP Traffic Flow . 27 LDAP Directory Hierarchy . 27 Zimbra Collaboration LDAP Schema. 28 Account Authentication . 31 Global Address List . 34 Flushing LDAP Cache . 36 Zimbra Mail Transfer Agent. 38 Incoming Mail Routing Overview . 38 Zimbra MTA Deployment. 38 SMTP Authentication. 39 Anti-Virus and Anti-Spam Protection . 40 Receiving and Sending Mail . 55 Zimbra Proxy Server . 57 Benefits of Using Zimbra Proxy . 57 Zimbra Proxy Components . 57 Proxy Architecture and Flow . ..