There are various tools available for the users to migrate mailboxes from source IMAP to office365 server. But, I recommend EdMails IMAP to office 365 Software particularly designed to work in multiple domains and allows the users to migrate IMAP to office365/ Exchange server effortlessly. The tool compatible with all IMAP email servers like Google mail – Gmail, Outlook.com, Office365.com, Yahoo Mail, Yahoo Mail Plus, Yahoo Mail UK, Yahoo Mail, Etc., both technical and non-technical can easily access this tool without any technical skill. The tool is well developed with some amazing features which can efficiently migrate all IMAP emails to office365. Competitor 

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