Zoho CRM/Zoho Mail Questions

Hi,

   We have a client that using zoho mail/CRM and have a few questions.

      Our mail is hosted with office365 and we want to intergrate it with zoho.

      We added the accounts to Zoho Mail using POP and we were told we can share each other email accounts in Zoho so that USER1 can see USER2 mailbox and vice versa (so that we can see all the outgoing emails and in the end, all 2 accounts are identical in terms of incoming and outgoing, just the login would be different).

     We were told this isn't possible, does anyone know if it is. We set the users accounts to PUBLIC in CRM and still, no go or I cannot figure out a way to view the other users accounts this way.

    Also we use to host our email with zoho mail but have moved them off of ZOHO. how can I get rid of the original mail account and just use zoho mail as a mail client (so USER1@email.com on OFFICE365 is visible, not the default USER1@email.com hosted on ZOHO).

   I was also told this isn't possilbe to remove it as I would lose function with ZOHO mail client and that I need to keep the mail client there.

   If this isn't possible, how can i rename the email accounts hosted on zoho mail so I don't see two " USER1@email.com" listed their but rather " USER1@email.com" and " USER1@doesnotwork.com"