IMAP Zoho mail accounts syncronization

IMAP Zoho mail accounts syncronization

Hi there,
I added some IMAP Zoho mail accounts to Zoho's colleague mail but the syncronization doesn't work very well.
When I select accounts from the colleague's account, mail to read are very different.
Example:
Access to the new mail by login in https://mail.zoho.eu : I see 3 e-mails to read
Access to the new mail by select from colleague's accountI see 7863 e-mails to read
There are the same e-mails, folders and tags but not "e-mail to read".
Why? How Can I solve?

Thanks in advance