How to install drupal/swiftmailer in Drupal8?

Question

Drupal

I'm trying to set up sending emails via swiftmailer according to the instructions
https://niklan.net/blog/131
The command to install swiftmailer
composer require drupal/swiftmailer:~1.0 fails. It always gives the
following:
Problem 1
- The requested package drupal/swiftmailer could not be found in any version, there may be a typo in the package name.

Answer 1

You need to add the Drupal repository to your composer.json:
Or just add to the file:

"repositories": {
        "drupal": {
            "type": "composer",
            "url": "https://packages.drupal.org/8"
        }
    },