📫 MIME Message builder

mime-msg-builder is a Rust library for building MIME Messages.

The core feature of the library is the Rust implementation of the Emacs MML module:

Creating a MIME message is boring and non-trivial. Therefore, a library called mml has been defined that parses a language called MML (MIME Meta Language) and generates MIME messages.

```eml From: alice@localhost To: bob@localhost Subject: MML simple

<#multipart type=alternative> This is a plain text part. <#part type=text/enriched>

This is a centered enriched part <#/multipart> ```

compiles to:

```eml Subject: MML simple To: bob@localhost From: alice@localhost MIME-Version: 1.0 Date: Tue, 29 Nov 2022 13:07:01 +0000 Content-Type: multipart/alternative; boundary="4CV1Cnp7mXkDyvb55i77DcNSkKzB8HJzaIT84qZe"

--4CV1Cnp7mXkDyvb55i77DcNSkKzB8HJzaIT84qZe Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit

This is a plain text part. --4CV1Cnp7mXkDyvb55i77DcNSkKzB8HJzaIT84qZe Content-Type: text/enriched Content-Transfer-Encoding: 7bit

This is a centered enriched part --4CV1Cnp7mXkDyvb55i77DcNSkKzB8HJzaIT84qZe-- ```

Definition

From the documentation:

The MML language is very simple. It looks a bit like an SGML application, but it’s not.

The main concept of MML is the part. Each part can be of a different type or use a different charset. The way to delineate a part is with a ‘<#part ...>’ tag. Multipart parts can be introduced with the ‘<#multipart ...>’ tag. Parts are ended by the ‘<#/part>’ or ‘<#/multipart>’ tags. Parts started with the ‘<#part ...>’ tags are also closed by the next open tag.

[…]

Each tag can contain zero or more parameters on the form ‘parameter=value’. The values may be enclosed in quotation marks, but that’s not necessary unless the value contains white space. So ‘filename=/home/user/#hello$^yes’ is perfectly valid.

Examples

See ./examples:

sh cargo run --example

Features

Template builder
Multipart support <#multipart>…<#/multipart>
SinglePart support <#part>…<#/part>
Attachment support <#part filename=…>
Part encryption using custom system commands (default: gpg --encrypt --armor --recipient <recipient> --quiet --output -)
Part signing using custom system commands (default: gpg --sign --armor --quiet --output -)

Development

The development environment is managed by Nix. Running nix-shell will spawn a shell with everything you need to get started with the lib: cargo, cargo-watch, rust-bin, rust-analyzer…

```sh

starts a nix shell

$ nix-shell

builds the lib

$ cargo build ```

Contributing

If you find a bug, feel free to open an issue at ~soywod/mime-msg-builder.

If you have a feature in mind, feel free to send a patchset at https://git.sr.ht/~soywod/mime-msg-builder/send-email or use the command git send-email.

You can also contact me directly on Matrix at @soywod:matrix.org.