Sucessful upload through round cube w/ 10MB file, then failed attempt with 650MB

[openletter]

You would have had to read the user’s previous topic to know the goal is importing emails from a different provider.

Import old email as MBOX or EML?

I am 16% done with backing up my email. Which does miab prefer to import with? Is it done through the web gui? Do I need a client like Thunderbird? What’s the least painless and most practical way to do this?