How do I log incoming email to Zoho Recruit when using an external provider

How do I log incoming email to Zoho Recruit when using an external provider

Hi there, 

We are currently using Zoho One but use Office 365 for our email.

We have been using Zoho Recruit to manage volunteer applications and vetting. 

Please can you advise on how we are able to log incoming email to a candidates record? Our sent email seems to log ok if we send from within Zoho Recruit or add the BCC email to an external email.