Mboxray
Open an mbox file from Gmail, Apple Mail or Thunderbird. Read it, search it, and save any message as a PDF.
Your mail is opened here, in this browser tab. It is never uploaded, and pictures that emails try to fetch from the internet stay blocked.
Drop mbox files or an Apple Mail export here, or
Open as many as you like. Each one gets its own place in the sidebar.
Getting an mbox file out of your mail
Gmail
Go to Google Takeout, choose Mail, and create an export. Google sends you a link to a zip file. Inside it, under Takeout and then Mail, is a file called All mail Including Spam and Trash.mbox. Open that one. Your labels come with it, so you can search them with label:.
Apple Mail
Select one or more mailboxes, then choose Mailbox, Export Mailbox. Mail saves each one as a folder ending in .mbox. Drop the folder here, or use Choose an Apple Mail export folder, and every mailbox inside gets its own place in the sidebar.
Thunderbird
Thunderbird already keeps each folder as an mbox file. Choose Help, Troubleshooting Information, and next to Profile Folder click Open Folder. Your mail is in the Mail folder, or ImapMail for an IMAP account, where each file with no extension is one folder of mail. Open that file, not the .msf file beside it. An IMAP folder holds only the messages Thunderbird has downloaded.
Outlook
Outlook for Windows keeps mail in PST files rather than mbox, and Mboxray cannot open those.
What happens to your mail
Nothing leaves this browser tab. Your computer reads the file a piece at a time, and it is never uploaded. We never see it, and there is no copy anywhere but the file you opened.
That is not a promise we keep by being careful. The page tells your browser to refuse every connection it did not make itself, so even an email that tries to fetch something cannot. Once the page has loaded, you can disconnect from the internet and it keeps working.
Emails are full of pictures that load from the sender, and loading one tells the sender you opened the message. They stay blocked. If you want to see them, you can load them for one message, and only that message reaches out.
Reloading the page forgets everything, including which files you opened.
Questions people ask
How big a file can it open?
Several gigabytes. The file is read in pieces, so it never has to fit in memory at once. A quarter of a gigabyte is listed in a few seconds. The first search through the text of every message takes longer, about twenty seconds for fifty thousand messages on a laptop, and matches appear while it runs. Searches after that are almost instant.
How do I save a message as a PDF?
Open it and choose Save as PDF, or tick several and choose Export as PDF. Your browser's print window opens: choose Save as PDF as the destination. Each message starts on a new page.
Can I save the attachments?
Yes. Each attachment is listed under its message, and clicking one saves it.
Can I open more than one file?
Yes, one after another. Each file becomes a mailbox in the sidebar and remembers where you were in it.
Does it work on a phone?
Yes, although a large archive is easier on a computer, which has more memory to work with.
What does it cost?
Nothing, and there is no account to make.