Zoho Mail does not sync all the email in iPhone through Exchange(msync.zoho.com)

Zoho Mail does not sync all the email in iPhone through Exchange(msync.zoho.com)

Hi,
I started using recently Zoho Mail and It seems fantastic, I mean almost or the best out there. I don't understand why others repute is as bad.
I started using Zoho Mail through IMAP and also through msync.zoho.com as Exchange account. The problem is that through Exchange all my mails are not synced on the iPhone. I have changed on the settings on the 1 week limit and selected as No limit which should then sync all the email. But most of my emails are not synced when I use as an Exchange account. I want to use through that because of the Push Notifications.

P.S. through IMAP everything works fine!

Thank you everyone who can help me out.