Note I'm happy to review and approve pull requests to update this plugin for Craft 4, but am not actively supporting it.
Campaign Monitor Transactional email adapter for Craft CMS enables you to send emails from the control panel via your Campaign Monitor account.
To install:
composer require clearbold/craft-campaignmonitor-transactional
To use:
Enable Campaign Monitor Transactional as your Transport Type under Settings > Email Settings in your Craft control panel. Then enter in the API key from your Campaign Monitor account.
Note that Campaign Monitor Transactional Email requires a monthly subscription.