Need help finding the the best method intergate email in CRM

Need help finding the the best method intergate email in CRM

We use Office365 online exchange, our sales person would like to have CRM keep track of incoming & outgoing email with clients in CRM, we tried few options below and still can't find best solution, hope some one can give me advices, thanks.
Below are what I had tried:

POP3: we like this setup, but the issue was it kept changing "unread" email status in user's Outlook to "read", and that is normal for POP3 (not zoho issue)

Plug-in for Microsoft Outlook: Seem ok, but users has to do everything manually (etc, add client's email manually into Zoho in Outlook)

IMAP Integration: I can only see email if I sent using Zoho, I can't see any incoming email.