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If you want to download IMAP emails to MSG files then download and use eSoftTools backup and migration software. When the internet is unavailable users can't open their IMAP emails but by saving emails as MSG files users becomes able to see their IMAP account email messages locally with MS OUTLOOK. This software helps you to transfer data in a minimum time period. This tool is the most trusted tool for transferring data from IMAP account to local drive.

Know More - Export IMAP emails to MSG file

https://www.esofttools.com/blog/export-imap-emails-to-msg-files/