Various MBOX-based email clients such as Thunderbird, Entourage, Seamonkey, Netscape, Gmail, Apple Mail, etc. do not allow the user to import mailboxes directly to Office 365. We recommend that users use the MailsDaddy MBOX to Office 365 migration tool to convert and migrate the database from MBOX to Office 365 account. This single software is enough to migrate databases from MBOX to Office 365 primary, in-place archive, and shared mailboxes. The software is capable of exporting large amounts of MBOX files to Office 365 mailboxes with attachments. The application comes with a free demo version to move up to 20 emails from each mailbox.

Read more: MBOX to Office 365 account