ficd.sh/content/blog/email-formatting.md

---
title: Email Formatting Is Harder Than It Looks
date: 2025-07-13
draft: true
---

*[UTF-8]: Unicode Transformation Format - 8 bit.

[Kakoune]: https://kakoune.org

As I've [mentioned before](./email-in-kakoune.md), I like using [Kakoune] for
reading & writing emails. Of course, Kakoune is a text editor, not a _rich text_
editor. It operates on UTF-8 _plaintext_ --- which means that the emails I write
need to be in plaintext, too.

As I went down this path, I quickly discovered that I needed an **email
formatter**. I eventually wrote [`mailfmt`](https://git.sr.ht/~ficd/mailfmt) to
fill this niche. It provides consistent paragraph spacing, hard-wrapping and
paragraph reflow, while preserving Markdown syntax, email headers, quotes,
sign-offs, and signature blocks. Additionally, the wrapped output can be made
safe for passing to a Markdown parser. This is useful if you want to build an
HTML email from plain-text.

`mailfmt` open-source under the ISC license, and is available on
[PyPI](https://pypi.org/project/mailfmt/) for installation with tools like
`pipx` and `uv`. The source code is available on sourcehut at
[git.ficd.sh/ficd/mailfmt](https://git.ficd.sh/ficd/mailfmt).

## Target Audience

I wrote this tool primarily for myself. It's served me very well over the past
few months. `mailfmt` could be helpful for anyone that prefers writing email in
plain-text using text editors like Kakoune, Helix, and Vim. It can format via
`stdin`/`stdout` and read/write files, making `mailfmt` easy to configure as a
formatter for the `mail` filetype in your editor.

I'm including a very lengthy explanation of exactly why I built this tool. You
may think it's overkill for such a small program — but I like to be crystal
clear about justifying my work. It reads like blog post rather than the
emoji-filled `README`/marketing style we're accustomed to seeing on this
platform. I've put a lot of thought into this, and I want to share my work. I
hope you enjoy reading about my thought process.

## Why I Built It (Comparison)

Unsurprisingly, it all started with a specific problem I was having composing
emails in plain-text format in my preferred text editor. As I searched for a
solution, I couldn't find anything that met all my needs, so I wrote it myself.

Here's what I wanted:

- A way to consistently format my outgoing emails in my text editor.
- Paragraph reflow and automatic line wrapping.
  - Not all plain-text clients are capable of line-wrap. In some contexts, such
    as mailing lists, the author is expected to wrap the text themselves.
- Inline Markdown syntax `can _still_ look great, **even** in plain-text!` Thus,
  I wanted to use it:
  - Without it being broken by reflow & wrap.
  - While looking good and retaining the same semantics in _both_ rendered
    **and** plain-text form — ideal for `multipart` emails.
- Ensure signature block is formatted properly.
  - The single space after `--` and before the newline **must** be included.

### `fmt` and Markdown Formatters Don't Work For Email

The `fmt` utility provides great wrapping and reflow capabilities — I use it all
the time while writing LaTeX. However, it's syntax agnostic, and breaks
Markdown. For example, it completely mangles fenced code blocks. I figured: hey,
why not just use a Markdown formatter? It supports Markdown (obviously), _and_
can reflow & wrap text! Here's the problem: it turns out treating your
**entire** email as a Markdown document isn't ideal.

`mailfmt`'s approach is simple: detect when a line matches a known pattern of
Markdown block element syntax, such as leading `#` for headings, `-` for lists,
etc. If so, **leave the line untouched**. Similarly, **don't format anything
inside fenced code blocks**.

#### Sign-Offs

Consider the following sign-off:

```
Best wishes,
Daniel
```

A Markdown formatter considers this to be one paragraph, and reflows it
accordingly, causing it to lost semantic meaning:

```
Best wishes, Daniel
```

Within the confines of Markdown, I counted three ways of dealing with the
problem:

1. Put an empty line between the two parts:

```
Best wishes,

Daniel
```

> However, this empty line looks _awkward_ when viewed in plain-text.

2. Put a backslash after the intentional line break:

```
Best wishes, \
Daniel
```

> Again, this looks bad when the Markdown isn't rendered.

3. Put two spaces after the intentional line break (• = space):

```
Best•wishes,••
Daniel
```

> This syntax is **ambiguous, easy to forget**, and **not supported by editors
> that trim trailing whitespace.**

`mailfmt` detects sign-offs using a very simple heuristic. First, we check if a
line has _5 or less_ words, and **ends with a comma**. If we find such a line,
we check the _next_ line. If it has 5 or less words **that all begin with an
uppercase letter**, then we assume these two lines are a _sign-off_, and we
don't reflow or wrap them. The heuristic matches a very simple pattern:

```
A courteous greeting,
First Middle Last Name
```

#### Signature Block

The convention for signature blocks is as follows:

1. Begins with two `-` characters followed by a single space, then a newline.
2. Everything that follows until the EOF is part of the signature.

Here's an example (note the • = space):

```
--•
Daniel

Software•Developer,•Company
email@website.com
```

As with sign-offs, such a signature block gets mangled by Markdown formatters.
Furthermore, the single space after the `--` token is important: if it's
missing, some clients won't recognize it is a valid signature — our formatter
should address this too.

`mailfmt` detects when a line's _only_ content is `--`. It adds the required
trailing space if it's missing, and it treats the rest of the input as part of
the signature, leaving it completely untouched.

### Consistent Multipart Emails

Something you may want to do is generate a `multipart` email. This means that
_both_ an HTML **and** plain-text representation of the _same_ email are
included in the file — leaving it up to the reader's client to pick which one to
display.

The plain-text email **must** be able to stand on its own, and _also_ render to
decent-looking HTML. Essentially, you want to write your email in plain-text
once, ensuring it has proper formatting, and then use a command to generate an
HTML email from it. For this, `mailfmt` provides the `--markdown-safe` flag,
which appends backslashes to the formatted output, making it safe for Markdown
parsing without messing up the line breaks after sign-offs and signature blocks.

For example, I use the following in [aerc](https://aerc-mail.org/) to generate
an HTML multipart email whenever I want:

```ini
[multipart-converters]
text/html=mailfmt --markdown-safe | pandoc -f markdown -t html --standalone
```

## Conclusion

If you've made it this far, thanks for sticking with me and reading to the end!
Even if you don't plan to write plain-text email or use `mailfmt` at all, I hope
you learned something interesting.