This is just a helper package designed to alias the acelaya/acmailer package name to acelaya/zf2-acmailer in packagist.
You can go to AcMailer to see the repository containing the actual code.
Due to some security restrictions of composer and packagist, it is not possible to rename a package that has already been published.
AcMailer was first released a lot of years ago, in 2014, when Zend Framework 2 was the latest version of what's today known as Laminas.
Since it was initially designed as a ZF2 module, I named it zf2-acmailer. It was obviously a bad idea.
The name of the package was already wrong when the new and shiny Zend Framework 3 was released, and now with the re-brand to Laminas, the name is plain wrong.
Because of that, and in order to avoid loosing all the history in packagist, I have decided to publish this small package, which requires acelaya/zf2-acmailer and replaces it, so that you can install acelaya/acmailer (which is a more generic and future-proof name) and still get the same.