Howto: Import Zimbra 8.8.15 Contacts & Calendars into Carbonio Release 22.7.2 CE

Hello.

I'm Carbonio's newest user, I just installed the latest version as of today's date.

I'm migrating from Zimbra 8.8.15 OSE to Carbonio CE.

I was able to use imapsync to populate my new install of Carbonio from my Zimbra instance. Worked very well to my surprise.

I'm unable to determine how to import my Contacts and Calendars into Carbonio.

I have exported them from Zimbra 8.8.15:

I export my 'just' my Contacts from Zimbra Web GUI, and it creates a tar-ball 'mystuff.tar.gz'

On the command line for Carbonio, I use the following to import them (Thinking much things under the hood look like zimbra, so....)

zmmailbox -z -t 0 -m me@my-new-carbonio.com postRestURL "//?fmt=tgz&resolve=replace" mystuff.tar.gz
ERROR: zclient.IO_ERROR (Connection refused) (cause: java.net.ConnectException Connection refused)

However, this does not work on Carboion, but it works on Zimbra 8.8.15

On the carbonio web interface, under Contacts there is an 'upload file', I tried to upload the Zimbra tar ball, and I also tried to upload Contacts.csv file exported from Zimbra, but my Contacts on Carbonio remain empty.

What am I missing?

What I've done. Searched this form. Searched the Internet. I can only find articles on importing from an Outlook PST file.I don't use Outlook, so I'm not sure if this can be done inside a 100% Linux environment?

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From: Zimbra 8.8.15/Ubuntu 20.04 (Release 8.8.15.GA.4179.UBUNTU20.64 UBUNTU20_64 FOSS edition, Patch 8.8.15_P33.)
To: Carbonio (Release 22.7.2 Community Edition.)