Microsoft created a user when trying to get win10 to update in May 2017. I deleted user 2-5-18, it deleted/removed messages from end of May until Jan 28 2018. Where are messages, what file type are they mail_data?
All your eM Client data is stored in C:\Users_username_\AppData\Roaming\eM Client. Deleting the user would have deleted that folder, so all email messages stored in local folders would have been deleted.
You may be able to recover the deleted user profile by following these instructions: https://www.easeus.com/file-recovery/recover-deleted-user-profile-and-files-in-windows-10.html
If you are able to recover, then just copy the database directory from the old profile to the new one.