Once you have decided to migrate Exchange mailboxes to Office 365, then use the Bitdataconversion Exchange Migration Tool. This tool migrates Exchange to Office 365, Live Exchange Server, Configured Outlook Profile, Outlook PST, Office 365 to Office 365 and Exchange to Exchange as well. This tool also provides a filter option that provides the facility to filter items based upon date, item type, etc. Option to mailbox mapping is also available. It can also map the mailboxes manually and automatically to the source with the destination according to the user's needs. It supports all the versions of Exchange Server and MS Outlook. A free demo/trial version of the software is also available that allows the migration of the first 50 items per folder.
For more information visit - https://www.bitdataconversion.com/exchange-migration.html