Depends of may factors, I suggest to evaluate:
- Number of mailboxes.
- How do you access email (Pc, Mobiles, Webmail).
- Do you need control of mail server (Set max attachment size, max mail per hour, filter recipients, etc).
- Do you prefer to pay for mailbox or a plain price for a dedicated mail server where you can create as many mailboxes as server support?
- Do you need to get reports of use ?
I would recommend Outlook that comes with Office 365.
Regards,
Adrian