Replying to a text/plain-only message generates unfa... | thunderbird/thunderbird-android

Nobody has claimed this yet.

Describe the bug
When replying to a message containing only a text/plain part and K-9 Mail is configured to send HTML messages, the app will generate HTML that puts the quoted text inside a <pre> tag. This leads to long lines not being wrapped in other clients. It works in K-9 Mail because we add the class k9mail to the tag and add a CSS rule for that class when displaying messages. However, this CSS style is not included in the message.

To Reproduce
Steps to reproduce the behavior:

Receive a text/plain message, e.g.

Date: Sun, 22 Aug 2021 17:14:52 +0200
From: <alice@domain.example>
To: <bob@domain.example>
Subject: Long line, text/plain
Message-ID: <msg001@domain.example>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

A line extremely extremely extremely extremely extremely extremely extremel=
y extremely extremely extremely extremely extremely long long long long lon=
g long long long long long long long long long long long long long long=2E

Make sure Settings > [Account] > Sending mail > Message format is set to HTML.
Reply to the message from step 1

The resulting message looks similar to this:

Date: Sun, 22 Aug 2021 17:16:03 +0200
From: Bob <bob@domain.example>
To: <alice@domain.example>
Subject: Re: Long line, text/plain
User-Agent: K-9 Mail for Android
In-Reply-To: <msg001@domain.example>
References: <msg001@domain.example>
Message-ID: <msg002@domain.example>
MIME-Version: 1.0
Content-Type: multipart/alternative;
 boundary=----G7YE98IGHS1BNE3I2L90D9ODGHKSOP
Content-Transfer-Encoding: 7bit

------G7YE98IGHS1BNE3I2L90D9ODGHKSOP
Content-Type: text/plain;
 charset=utf-8
Content-Transfer-Encoding: quoted-printable

What is K-9 Mail doing with this when replying?

On August 22, 2021 5:14:52 PM GMT+02:00, <alice@domain=2Eexample> wrote:
>A line extremely extremely extremely extremely extremely extremely extrem=
ely extremely extremely extremely extremely extremely long long long long l=
ong long long long long long long long long long long long long long long=
=2E

------G7YE98IGHS1BNE3I2L90D9ODGHKSOP
Content-Type: text/html;
 charset=utf-8
Content-Transfer-Encoding: quoted-printable

<html><head></head><body>What is K-9 Mail doing with this when replying?<br=
><br><div class=3D"gmail_quote">On August 22, 2021 5:14:52 PM GMT+02:00, =
&lt;alice@domain=2Eexample&gt; wrote:<blockquote class=3D"gmail_quote" style=
=3D"margin: 0pt 0pt 0pt 0=2E8ex; border-left: 1px solid rgb(204, 204, 204);=
 padding-left: 1ex;">
<pre dir=3D"auto" class=3D"k9mail">A line extremely extremely extremely ex=
tremely extremely extremely extremely extremely extremely extremely extreme=
ly extremely long long long long long long long long long long long long lo=
ng long long long long long long=2E<br></pre></blockquote></div></body></ht=
ml>
------G7YE98IGHS1BNE3I2L90D9ODGHKSOP--

Screenshot

In Thunderbird the message is displayed like this:

Expected behavior
Use HTML that leads to the message being displayed in a sensible way by other clients. We probably shouldn't put the quoted text inside a <pre> tag.

I'm guessing the main problem is that we don't distinguish between HTML for local display and HTML that is included in outgoing messages.

Environment:

K-9 Mail version: 5.900-SNAPSHOT (97b53fb685a0c6522c28bdaa5fbd5a141c036a06)

No file or test is identified in the issue. Start by tracing reply HTML generation and the distinction between locally displayed HTML and HTML included in outgoing messages; done means replies to text/plain-only messages render sensibly in other clients without relying on K-9 Mail-specific styling.

Written by the indexing model from the issue text.

Replying to a text/plain-only message generates unfavorable HTML

Description

Contributor guide

First steps

Research direction

Assessment