Thunderbird stores email messages locally, and users can export mailbox data in MBOX format for migration. First, locate the required Thunderbird profile folders and identify the MBOX files containing your emails. Keep a copy of the original files before starting the transfer. A suitable migration utility can make the process easier by allowing users to load MBOX files and preview their mailbox content. The Aryson MBOX Migration Tool provides options to select MBOX files, preview emails and attachments, and choose Office 365 as the destination. Users can also process multiple MBOX files and apply date filters when selecting messages. To migrate MBOX to Office 365, provide the required account details and review the selected destination before starting. After migration, check the Office 365 mailbox to confirm that the expected emails and folders are available. This approach can help individuals and organizations manage Thunderbird email migration in a more organized way without manually transferring individual messages.