If you have the emails related to your business and now you want to switch your whole mailbox into Office365 for further uses. There are some easy modes to achieve the transfer of Emails of 1 & 1 Webmail to Office365. Multiple users getting confused between free and premium tools. Major of them used free tools in which maximum of the fake and data stealer. That's why big companies and firms generally used the well recognized company’s product for example
eSoftTools which produces IMAP Backup and Migration Tool. They also provide a free demo and a 30 days money back guarantee for loyalty of their service.
Read more:-
https://www.esofttools.com/blog/1and1-webmail-to-office-365/