What's New in Mbox Viewer 2.8.2: Merging Mailboxes, Rebuilt

Mbox Viewer 2.8.2 has a single theme: merging mailboxes. It came out of a long, specific piece of feedback from someone who merges archives for a living, and every point in it turned out to be right. The Mac app (build 43) takes all eight; the Windows app takes the five that apply to it — one of them was already solved there back in 2.7.1, so on that point it is Mac catching up. The Mac one landed on the Mac App Store on 7 August and the Windows one on the Microsoft Store on the 8th: both are out.

As always, the app is read-only. Merging writes a brand-new mailbox and never touches the files you feed it.

Apple Mail exports are traceable again

Merging has an optional setting that stamps each message with the mailbox it came from, using an X-Mbox-Source header. It is the answer to the obvious worry about merging: if I combine ten archives, do I lose track of what came from where?

Except with Apple Mail exports, you did. “Export Mailbox…” doesn’t write a file called Inbox.mbox — it writes a folder called Inbox.mbox with a file inside it named, literally, mbox. That inner file is the one being read, so every message from every exported mailbox got tagged X-Mbox-Source: mbox. The header was there, it just said nothing.

Merged messages now carry the name you actually recognize — Inbox.mbox, Sent.mbox — and two mailboxes that would end up with the same name are told apart by the folder above them: Work/Inbox.mbox and Personal/Inbox.mbox. This one is fixed in the shared engine, so both apps get exactly the same behaviour.

Merging without opening a mailbox first (Mac)

On the Mac, merge used to live inside a document window, which made for a strange dance: open a mailbox, choose Merge, then manually add that same mailbox to the list before adding the second one. You had to start from a file you didn’t necessarily care about.

It is now an app-level action with its own window, in File → Merge MBOX Files… and as a button on the welcome screen, with nothing open. If you do have a mailbox open, it starts out in the list already. On Windows this has worked from the settings menu since 2.7.1, open mailbox included — here it’s the Mac that was behind.

Knowing what the merge is doing

Both apps used to go quiet exactly when you most wanted a sign of life. They fixed it in the shape each one needed.

On the Mac, the whole window was rebuilt: the mailbox list scrolls instead of growing past the bottom of your screen, each mailbox shows its size with a running total (2 mailboxes · 257 MB), you can drop files straight onto it, and it reports real progress — Merging 2 of 5 — Inbox.mbox. When it finishes it says how it went in your own language (it used to report in English regardless) and swaps the buttons for Show in Finder, Open Merged Mailbox and Close. Before, there was no clear way out of a finished merge.

On Windows, the progress bar was indeterminate with a fixed label, even though the engine had been reporting progress all along. It now names each mailbox as it goes — Merging 2 of 5: Inbox.mbox, the same name that gets written into the header — and when it’s done the status bar shows the full path of the merged file. Before, you only saw its name in the tab.

Small things that added up

The rest of the review went into details that each cost you a few seconds, over and over:

• Two Mac toolbar buttons looked identical. Conversation threading and Search Filters shared an icon; threading now uses the conversation bubbles Mail uses for the same idea.
• Tooltips. On the Mac, the six icon-only view buttons — Text, Full Headers, Properties, MIME, Raw, Hex — could only be decoded through the View menu; they now name themselves on hover, shortcut included: “Full Headers (⌘2)”. On Windows, fifteen controls had no explanation at all — the search box, the sort dropdown, the welcome-screen buttons, the viewer tabs, the buttons on each attachment — and Export and Print now show theirs too (Ctrl+E / Ctrl+P).
• Clicks that did nothing. On the Mac, menu items that need an open mailbox are greyed out instead of silently ignoring the click. On Windows, the same for “Repair mailbox” and “Export repaired copy” in the settings menu — Merge stays available, because it works either way.
• Windows Help now explains merging, in a new “Merge mailboxes” section: what “Remove duplicates” does, what the X-Mbox-Source checkbox writes, and how to actually see that header in a message.

The same fix, upstream

Mbox Viewer is built on mboxShell, the open-source terminal tool at the heart of the app. The Apple Mail naming bug lived there too, and mboxShell 0.6.2 fixes it in the same way — that is the engine the Windows app now ships. There’s also a documentation fix worth knowing if you use the CLI: merge deduplicates by default, and the real flag is --no-dedup. The --dedup flag the docs described never existed.

Getting it

2.8.2 is out on both the Mac App Store and the Microsoft Store, where it arrives as a normal update. And if you’d rather read the full list first, it is on the changelog.