Question 1

How do I open a Google Takeout mail export?

Accepted Answer

Unzip the Takeout download, open the Takeout and Mail folders, and drop the .mbox file on this page. Gmail's labels come with it, so you can still pick out the Inbox, Sent mail or any label you made.

Question 2

Where are Thunderbird's and Apple Mail's mbox files?

Accepted Answer

Thunderbird keeps each folder as a file with no extension, such as "Inbox" or "Sent", in the Mail folder of its profile; that file opens here as it is. Apple Mail's Mailbox, Export Mailbox makes a folder ending in .mbox, and the file inside it named "mbox" is the one to open.

Question 3

Does it search inside the messages?

Accepted Answer

It searches subjects, senders and recipients. Searching every message's text would mean reading the whole mailbox through again for each search, which is slow for a large export.

Question 4

Can I turn the mailbox into a PST for Outlook?

Accepted Answer

No, this page only reads the mailbox. You can save the messages you need as .eml files, which Outlook opens one at a time.

Question 5

Is my mailbox uploaded anywhere?

Accepted Answer

No. The file is read by this browser tab, a piece at a time, on your own device. A mail export holds years of private messages, which is a good reason not to upload one to a website.

Free online MBOX viewer: read a Gmail export or mailbox file