Copy sent items of user mailbox to shared mailbox

Hello everyone,

I'm currently testing a mail scenario with Exchange Online Plan 1. The general idea is having 1 info@ address as a shared mailbox and about 5 user@ addresses with accounts.

All incoming mails should go into the inbox of the shared mailbox (that works, no problem), but also all outgoing mails should be placed in the sent items of the shared mailbox. Internal work flow requires that behaviour. 

Since 2013 it seems possible to adjust the settings of the server to actually copy the sent item of a shared mailbox address to the sent items folder of the shared mailbox without registry hack - that sounds good (haven't testet it yet). 

Now I have two questions:

1. Does this also work with Exchange Online Plan 1 (since I don't have a power shell there...) ?
2. How can I also copy the sent items of the user@ addresses to the shared mailbox sent items folder?

I tried using the local outlook rules, but those seem to be stuck within one mailbox. I can't actually copy a sent item from the personal mailbox to the shared mailbox using a rule...doing it manually works though. 

Any help would be appreciated!