Add mailcrab.

mailcrab enrty under email tools

README.md

@@ -1201,6 +1201,7 @@ See also [About Rust’s Machine Learning Community](https://medium.com/@autumn_
 * [jdrouet/mrml](https://github.com/jdrouet/mrml) - A library to generate nice email templates working on any mail client.
 * [lettre/lettre](https://github.com/lettre/lettre) — an SMTP-library for Rust [![CI](https://github.com/lettre/lettre/actions/workflows/test.yml/badge.svg?branch=master)](https://github.com/lettre/lettre/actions/workflows/test.yml)
 * [mailtutan/mailtutan](https://github.com/mailtutan/mailtutan) An SMTP server for test and development environment.
+* [tweedegolf/mailcrab](https://github.com/tweedegolf/mailcrab) — Email test server for development.
 * [staktrace/mailparse](https://github.com/staktrace/mailparse) [[mailparse](https://crates.io/crates/mailparse)] — A library for parsing real-world email files
 * [stalwartlabs/mail-auth](https://github.com/stalwartlabs/mail-auth) [[mail-auth](https://crates.io/crates/mail-auth)] - DKIM, ARC, SPF and DMARC message authentication library [![build badge](https://github.com/stalwartlabs/mail-auth/actions/workflows/rust.yml/badge.svg)](https://github.com/stalwartlabs/mail-auth/actions/workflows/rust.yml)
 * [stalwartlabs/mail-parser](https://github.com/stalwartlabs/mail-parser) [[mail-parser](https://crates.io/crates/mail-parser)] - A fast and robust e-mail parsing library with full MIME support [![build badge](https://github.com/stalwartlabs/mail-parser/actions/workflows/rust.yml/badge.svg)](https://github.com/stalwartlabs/mail-parser/actions/workflows/rust.yml)