If you want a solution that easily convert mailbox from MBOX-based email clients to Office 365 format then you can try MailsDaddy MBOX Converter tool. This single program has lots of conversion options including Office 365 account. It easily transfer data from MBOX-based email clients to Office 365 with all mail and attachments. You can download free demo edition of the solution and export up to 20 items from each folder.
MBOX to Office 365
