To export an Office 365 mailbox to PST using the Cigati Office 365 Backup Tool, first download and install the software on your Windows system. After launching the tool, sign in using your Microsoft 365 or Office 365 account credentials. Once the mailbox data is loaded, select the required mailbox folders such as Emails, Contacts, Calendars, Tasks, and Attachments. Next, choose PST as the saving format and specify the destination location on your computer where you want to save the exported file. The software also provides advanced features like date filters, duplicate email removal, split PST options, and selective mailbox backup for better management. Finally, click on the Backup or Convert button to start the export process. The tool securely exports Office 365 mailboxes to PST while preserving folder hierarchy, metadata, and attachments without data loss.