EagleFiler encountered an unexpected error (probably due to a bug), so I have no idea what the problem is. If you could send me a Zip archive of the IMAP mailbox you were trying to import from, I can try it here and find the source of the problem. The mailbox would be stored as a folder whose name ends with “.imapmbox”, and it would be inside a folder named after your account, inside the folder:
I’m having problems expanding the Zip file that you sent. How did you create it? It’s 25 MB, but when I expand it (and some errors are reported) it’s only 6 MB and does not seem to be a valid .imapmbox. Could you create a smaller mailbox with just a few messages and send me a Zip of that?