Do not recommend
The app loads emails in a strange and arbitrary order and there is no option to sort messages, which is something every email client does. The app also stalls when there is a lot of data to deal with, suggesting it doesn’t actually scale all that well.
Response from developer
We code and ship user requests in less than 24 hours. Full sorting by Date, Sender, Subject, and Size is now available. Our tests show the app smoothly handles even 250 GB MBOX files without stalling, but we optimized the engine even further. The update is currently awaiting Apple's approval. Thank you for the feedback.