Yes, you can migrate at any time. The administrator of the organization that is using the Zoho Mail Free Plan can export their data from the Zoho Mail Admin Console by following the instructions given here.

Alternatively, you can also activate trial from the administrator account (login to your Zoho Mail account, click on your profile icon and activate trial) and enable POP/IMAP access to migrate data from Zoho Mail. You can also get in touch with us at support@zohomail.com and we’ll help you through the process.