"collaborative inbox" (like Gmail)

Hello Chris, thanks for your feedback.
yes, I know the new microsoft groups (we all haveO365), which I think is a clever solution for building working groups dedicated to projects or initiatives not too complicated.

But honestly they do not seem suited to handle the job everyday....:

We are a national association and do consulting activities/services to our associated companies.
Every day we receive many emails from both associated companies and other customers.

Many relate to simple questions, while others need further attention to provide a complete answer.
There is rarely a need to build a real working group.
So we must find an intelligent system to ensure that:

- All employees can have access to a shared inbox (at the moment not set up yet)
- Anyone can take charge of an email, in this case he/she became the owner of the task and is in charge of it.
- no incoming email left behind and thus with no follow-up
- Remain track of the work done by employee
- The manager can change the assignment work

- Archive the practice. and possibility to access past email to study
- and so on.
Seen in this way, it seems a ticketing system. However, the "collaborative inbox" google to me just do that !
I think MS has tool and solution for all but not for simple things !! :-)

Among other things we are still looking for guidelines, or suggestions, to set up a "smart" configuration of our accounts, in order to collaborate SIMPLE between us. Possible that nobody has this kind of problem and the only way to collaborate is to send email to all in CC ? :smileyfrustrated:
Thanks for any advice you want to give us.

Stefano