1961349 - got mbox line >>>>>>From

Status: RESOLVED DUPLICATE of bug 1976143

(Thunderbird :: Untriaged, defect)

Description

[Martin B.]

Attachment: temp_mbox.zip - mbox file with the problematic message

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:137.0) Gecko/20100101 Firefox/137.0

Steps to reproduce:

I have a lots of emails stored in Thunderbird's local folders but also some IMAP accounts configured in Thunderbird.
OS: latest Ubuntu 24.10
Thunderbird: 128.9.1esr (64 bit) from snap

Recently I tried to move some emails from local mbox to Proton Mail (via their Proton Mail Bridge) running on the laptop. But I wasn't able to move the email. After some discussion with Proton support, it turns out that there is incompliant headers in the emails (see one of those emails full headers below). The X-Mozilla-Keys row is full of spaces, folllowed by newline character (^M). The following line start with ">>>>>>" and this is the reason why Proton Mail Bridge refuses to move this email to Proton account.

What is the problem? Thunderbird never complained about the email.

From - Wed Feb 12 10:20:14 2025^M
X-Mozilla-Status: 0001^M
X-Mozilla-Status2: 00000000^M
X-Mozilla-Keys: ^M

From [e-mail] Tue Oct 2 21:48:26 2007^M
Subject: Dotaz k =?ISO-8859-1?Q?placen=ED?= =?ISO-8859-1?Q?_pojistn=E9ho?=^M
From: Martin =?ISO-8859-1?Q?Bodl=E1k?= <[e-mail]>^M
To: [e-mail]^M
Content-Type: text/plain; charset=UTF-8^M
Message-Id: <[e-mail]>^M
Mime-Version: 1.0^M
X-Mailer: Evolution 2.10.3 (2.10.3-4.fc7) ^M
Date: Tue, 02 Oct 2007 21:48:26 +0200^M
X-Evolution-Format: text/plain^M
X-Evolution-Account: [e-mail]^M
X-Evolution-Transport: smtp://smtp.warnet.cz/;use_ssl=never^M
X-Evolution-Fcc: mbox:/home/mbodlak/.evolution/mail/local#Sent^M
X-Evolution-Source: local_mbox^M
Content-Transfer-Encoding: 8bit^M

I also tried to ask in support forums but I got asked to fill a bug.

Actual results:

I received an error from the Proton Mail Bridge. After contacting Proton support, they concluded:

It is not correctly formatted for it to be related to that header.
The header key and value should be on the same line, e.g. like this: 

X-Mozilla-Keys: >>>>>>From [e-mail] Tue Oct 2 21:48:25 2007

However, in the message, they are separated into two lines.
X-Mozilla-Keys:

From [e-mail] Tue Oct 2 21:48:25 2007

This is, unfortunately, not compliant with the RFC standards for email, so the message fails the validation. We apologize for the inconvenience.

Expected results:

I would like to have those emails correctly moved via IMAP protocol to Proton Mail account.

Comment 1

[Alfred Peters [:infofrommozilla]]

Everything is fine with the X-Mozilla-Keys: header as it is here.

But this line is indeed wrong:

>>>>>>From [e-mail] Tue Oct  2 21:48:26 2007^M

A line beginning with FROM (without a colon!) indicates the separator line between two e-mails in the MBox database format.
If an e-mail containing such a line in the body is imported, it is escaped by adding a “>”. Lines that already begin with one or more “>” are given an additional “>”. This “>” should be removed again when reading out.
Of course, this should not happen in the header area, as this does not create a valid header.

I can only assume that somehow an MBox file was saved to the database instead of an e-mail. Its separator line has then grown to the line you see.

To work around the problem, you can export the e-mail from TB, delete the line there and then import it again.

Comment 2

[Martin B.]

Thank you for an explanation. I also understood your workaround proposal.

Comment 3

[Martin B.]

BTW, is it something which could be somehow made part of the "cleanup" command? I suppose now it removes deleted messages from mbox etc. and I wonder if this check can be part of this "etc."

I fully understand that there might be a lot of various defects related to the mbox content.
The fact also is that I don't recall any possible way how I could have caused this to happen.

Comment 4

[Alfred Peters [:infofrommozilla]]

(In reply to Martin B. from comment #3)

The fact also is that I don't recall any possible way how I could have caused this to happen.

Well, the e-mail is from 2007, which is quite a while ago... 😉

Comment 5

[Alfred Peters [:infofrommozilla]]

Bug 1976143 describes a way in which this bug can still be reproduced. I am therefore closing this bug as dupe of Bug 1976143.