If you want to backup Maildir files/folders into any other file format, then
always use Maildir Backup Tool. This tool definitely supports the backup process
into PST, PDF, MSG, MBOX, EML, EMLx, Office 365, Outlook.com, Gmail, G Suite,
Exchange Server, and so on. The software comes with some amazing features and
benefits to its performers as like- batch process, preview feature, save email
attachments, etc. All Windows versions are suitable to download this program.
Free download edition available as an additional benefit.
Read More:
https://www.cubexsoft.com/blog/maildir-backup/