One true solution for collaboration is the Zimbra Email Collaboration Server. Latest Zimbra is at version 8.8. Besides an E-mail Server, Zimbra Collaboration comes with a calendar solution and it offers Synchronization with mobile devices. For synchronization with MIUI 10 Calendar, first you need to install CalDav Sync Free Beta from Gege, from Google Play. CalDav After this, we proceed with starting the calendar app: On the top, right corner, click the gear to enter calendar settings: Click on the calendar accounts: Click on Add account: From this list choose CalDav Sync Adapter There, you fill in the blank fields, with username, a password and an url address of the Zimbra Collaboration Server, something like http://servername.com. Sign in or register and you are almost done. Now that you have configured your CalDav account, you need to go to setting, accounts, sync section: Then choose Caldav Sync Adapter: Click on the account