force email sync to CRM

hey guys.

I've noticed sometimes that CRM doesn't sync emails, during a short period of time (hours).

-> is there a way to force synchronization of emails to CRM (2013)? I know they didn't sync to CRM because I see them on my Outlook Inbox.

I'm using CRM 2013 on-premises, with SP1 w/ UR2.

Thanks in advance,

Regards,