Apple Mail cannot open imap-backup's mbox-files (with fix)

[bergfruehling]

Hi there,

I used imap-backup to save some older mails from my account and the download worked flawlessly. Thanks a lot for the tool.

However, Apple Mail is not able to import the stored .mbox-files. I debugged the issue with Gemini 3.5 and could solve it by removing the colon from the escaped (with >) From-Line. Gemini claims that the colon is not per standard. I have no other source for that, but only without the colon Apple Mail can open the .mbox-files.

Here is an example to make it clearer:

From mail@domain.de Sat Nov 14 20:26:54 2020
Return-Path: <mail@domain.de>
(more headers)
Date: Sat, 14 Nov 2020 20:26:54 +0100 (CET)
>From: "Name" <mail@domain.de>
Reply-To: noreply@domain.de
(it goes on)

The second last line should read (to be compatible with Apple Mail):

>From "Name" <mail@domain.de>

I used sed to fix it:

sed 's/^>From:/From:/' original.mbox > fixed.mbox

Can anybody else confirm that this format is working for ther clients? Then it might be worth changing the output?

Kind regards,
Henning

[joeyates]

imap-backup uses the mboxrd format for serialization.

Where you're seeing >From:, that's a header from the original email, with a > prepended (as per the standard).

Currently, imap-backup has a Thunderbird exporter. It might make sense to add an exporter for Apple Mail - PRs welcome!

[bergfruehling]

Thanks for the quick reply and the link. The link says:

In MBOXRD files, any line of the message, in either the header or the body, that begins with zero or more '>' characters followed by the five characters 'F', 'r', 'o', 'm', and ' ', has a single greater-than sign (">") character prepended to it. When a message is read from a MBOXRD mailbox file, it is transformed back so that any line of the message, in either the header or the body, that begins with one or more '>' characters followed by the five characters 'F', 'r', 'o', 'm', and ' ', has the single leading '>' character removed from it.

The link is very specific in that only "From " (followed by a space) shall be escaped. In my example above (which is from imap-backup's output) the line is escaped even though it read "From:". Thus, the escaping is wrong if the standard is applied strictly and Apple Mail does not de-escape the line.

To me it seems, that the serialization should be fixed. Then no exporter for Apple Mail would be needed. Or am I misinterpreting the format specs?

[joeyates]

You're quite right. This needs to be sorted out!

I've started working on a fix. I'll open an issue to track it.

[bergfruehling]

Great, thanks!

[joeyates]

I've opened issue #264

[kenthomson001]

Thanks for sharing this solution. Your fix for the Apple Mail MBOX import issue is very useful and may help many users facing the same problem.