SysTools Office 365 Backup & Restore is the best solution to perform Office 365 mailbox archive and import PST to Office 365/Exchange Online. This tool downloads complete mailbox data from Office 365 and saves it on the local server/hard drive. This utility exports all emails with attachments, calendars, contacts of multiple Exchange Online accounts of a domain to PST & EML file format. Another functionality of this software is that it also helps in migrating bulk PST to Exchange Online.