Two years ago we released the PST Capture Tool, which makes this process easier by locating PST files scattered across your organization, collecting them into one place, and then uploading the contents directly into Exchange Online mailboxes. But no matter how you cut it, moving dozens or hundreds of terabytes across your existing Internet connection is going to be a costly and lengthy process. We have consistently been approached by customers and partners asking for help with migrations that could easily take multiple years to complete, because of the time required to move data across the wire.
Continue reading about the new service at source: http://blogs.office.com/2015/05/07/making-email-archive-migration-easier-with-the-office-365-import-service/
Until later,
Henrik Walther