How to ensure email is retained within Bigin CRM Client record and / or Deal history if the user leaves.

I have read the link below for Zoho CRM. Is the same email setup required (POP3) if emails must be retained in the Bigin records after the user has left the business? Some current users have only gmail, is this still possible and if so, how?

Many thanks in advance

Alun

What happens with the email in the CRM when a user leaves the company and their email address gets deleted? (zoho.com)