PART 1

sudo apt install kmail

installs MariaDB during installation

it works, but it starts from the second time, the first launch occurs with an error in the parent collection - IT has ALWAYS BEEN so and has never been fixed by the developers, well, it WORKS

sudo apt install mysql-server

DELETES MariaDB during installation, KMail doesn't start now

PART 2

sudo apt install mysql-server

installs MySQL, we use It to create databases

sudo apt install kmail

DELETES MySQL during installation because it installs MariaDB (who will pay for deleted MySQL databases?)

QUESTION: Will someone ever write a NORMAL KMail instruction? Or does the stability of Linux consist in perpetual constant errors?

And I do not need the nonsense of the topics of this forum to give there's never anybody solved nothing.