I purchased the license for the Dovecot Object Storage for Dropbox to test this functionality on a personal domain. Unfortunately I can not make it work, I create the token for my Dropbox account from here https://dropbox.dovecot.fi/ and setup in dovecot configuration. When I try to login with an user I found these errors in log file: ===========Dec 27 10:52:16 mail dovecot: imap-login: Login: user=<dovecot1 at test.it>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=8844, secured, session=<xxCXDIHuTQB/AAAB> Dec 27 10:52:16 mail dovecot: metacache-worker(8839): Error: fs-dropbox: GET 1/metadata/sandbox/dovecot1 at test.it/idx/?file_limit=25000 failed: 401 Unauthorized Dec 27 10:52:16 archiviomail dovecot: metacache-worker(8839): Error: Failed to iterate dovecot1 at test.it/idx/: GET 1/metadata/sandbox/dovecot1 at test.it/idx/?file_limit=25000 failed: 401 Unauthorized Dec 27 10:52:16 mail dovecot: imap(dovecot1 at test.it): Error: user dovecot1 at test.it: Initialization failed: Namespace '': obox: USER-REF: /var/run/dovecot/metacache returned failure Dec 27 10:52:16 mail dovecot: imap(dovecot1 at test.it): Error: Invalid user settings. Refer to server log for more information. Dec 27 10:52:16 mail dovecot: imap-login: Login: user=<dovecot1 at test.it>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=8846, secured, session=<NTSaDIHuTgB/AAAB> ============ I do not think it's a problem of my configuration, if instead of Dropbox use AWS S3 works fine, seems to be a token problem (401 Unauthorized). The plugin configuration is this: ### Dropbox plugin { obox_fs = fscache 10G:/var/lib/dovecot/cache:dropbox:https://XXXX:YYYY at dropbox/ } Anyone successfully used this setup?