Every email program will store all messages for any account in a single file. We recommend customers ensure these files are regularly backed up, so as to make sure they have a copy of their emails and guarantee business continuity. The simplest way to back up these files is to export them from the email program, however advanced users can select the file in use within their computer backup software. Please find below links to guides on how to export the email files so they can be stored securely:

Microsoft Outlook 

Mac Mail