With the help of the Softaken Mail Importer, you can safely upload MBOX files into the IMAP server. This software is available for both Windows. It allows you to migrate one or more MBOX files in one go. This software ensures the security of file data and provides 100% secure migration. Its additional features help you to perform the MBOX file migration of a specific IMAP account. Also, you can use this tool to import MBOX files to Gmail, AOL, IMAP, Office 365, and other email clients with attachments. Furthermore, it offers a free demo version that can migrate a few emails per folder. Refer: https://www.softaken.com/mail-importer