The simplest way I found for importing lots of Thunderbird community folders is usually to build a temporary dovecot server, convert the thunderbird mail merchants to linux mbox mailstores and after that imapsync it with the temp server on the zimbra server: By leveraging migration aid resources, you may tackle https://free-webmail-zimbra-migra90000.mappywiki.com/716165/zimbra_migration_can_be_fun_for_anyone