Is the "shared mailbox" a must to enable TeamInbox, or does it work with a distribution list as well?

Is the "shared mailbox" a must to enable TeamInbox, or does it work with a distribution list as well?

Hi, 

I started with a distribution list for a team, as at this time it wasn't possible to create a shared inbox with the trial version. In the meantime I have the Zoho One licences and tried to setup the TeamInbox but it doesn't work. The mail I want to use for the team in the TeamInbox is the same as I already used for the distribution list. I wanted to change the distribution list to a shared mailbox, but I cannot find a way how to do it. Furthermore, I need the mails already existing in the mailbox (distribution list).
Does anyone have an idea how to solve the issue?

Thanks
Patrick