It is actually mbox. I should have provided more detailed numbers - in my Takeout file, for example, there are 91,360 chat messages and only 23,407 email messages .

So there's 23407 email messages but only one file containing all of them?

Yep! All messages are in a single mbox file and it's 3.2GB.

  cdubz@professor-farnsworth ~/data $ du -h Mail-chris.mbox 
  3.2G	Mail-chris.mbox

Wow. I stand corrected and that's awful. Yet another reason to use gmvault!

Why it awful? As an archive, seems decent.

(1) inconsistent escaping rules (dealing with the literal string \nFrom)

(2) easy to corrupt

Worth noting that Google provides some Python sample code for parsing the file which works great.

Interesting - could you point out where to find this? I poked around a bit but didn't come up with anything.