Note the rustmailer project mentioned is heavily proprietary licensed. Don't expect to be able to use any of this.
First, rustmailer is my GitHub username. Under this GitHub account there are two main projects: RustMailer and Bichon.
RustMailer is a middleware product with the same name. It is commercially licensed. I hope it can help developers save time on email-related development and also generate a bit of income for me, so this middleware requires a license key to run long-term.
Bichon, on the other hand, is an independent project built on the experience of developing RustMailer. It does reuse a lot of similar code, but it is licensed under the AGPL. These are two completely different projects. RustMailer provides many API interfaces similar to EmailEngine and is positioned as middleware, while Bichon is an email archiving (or unified search) project.
Bichon is positioned as a permanently free project. Users never need to worry that if you use Bichon today you will be asked to pay later — you can use it with confidence, and all of its code is fully open and transparent.
> RustMailer is source-available. The code is open on GitHub, but requires a valid commercial license key for production use.
License Purchase: https://rustmailer.com/pricing
The mention of BSD/Apache is from here[1] and looks to be a listing of open-source licenses that this project uses.
[1] https://github.com/rustmailer/rustmailer/blob/main/license.h...
It must not be using any RustMailer code.