IMAP Mails when an employee leave the company

IMAP Mails when an employee leave the company

Hello,

We are thinking of setting up our ZOHO CRM accounts with IMAP (Gmail).

If an employee leave the company, do we need to keep his Google account to keep his mails into CRM ?
If we remove his Google account, the employee emails will stay into CRM or they will be removed ?

If they are removed with IMAP, will they stay if we use POP instead ? 

Thanks a lot !

Jerome

Moderation update:
Kindly note that the option to take a backup of emails is now available in the CRM for users who have configured their email account via IMAP. 
Announcement post: 
https://help.zoho.com/portal/en/community/topic/introducing-zoho-crms-all-new-email-configuration
Help doc
https://help.zoho.com/portal/en/kb/crm/connect-with-customers/email/email-configuration/articles/email-configuration-for-imap-pop#Taking_Email_Backup