Using Rainloop Offline Without Connection

Hi,

I moved our mailserver to Yandex and changed the MX records, but I was hoping to be able to access and read old mails through rainloop. However, it doesn’t let you sign-in when it can’t connect.

Is there any way to access these old mails hopefully with rainloop or with any other method? Can I at least somehow download them from FTP? What folder are they in?

Or is it possible to change mail subdomain and keep it alive in background to be able to access old mails?