The common exchange formats for email are MIME (.eml) and Mbox (.mbox) which are both supported for import.
One multiple files with either MIME or Mbox data can be uploaded to add email messages to the currently selected folder:
Messages from your inbox or any other folder can be downloaded to your computer for archiving or backup. When exporting, messages will be saved as single .eml files.
To download an email message, select one first a message first in the Messages List and then choose Download (.eml) from the More menu in the toolbar. Choose where to save the exported .eml file if prompted, otherwise find the file the “Downloads” folder on your computer.
Multiple messages will be packed into a Zip file for downloading. Select individual messages in the Messages List and then follow the instructions for downloading a single message. You need to unpack the downloaded .zip archive to access the individual message files.
For archiving purposes all messages from a folder can be downloaded as .zip archive without first selecting them in the list.
Switch to the folder you want to export and then select Download folder from the Folder actions menu behind the gear icon in the folders list footer.