SendMailCommand not usable inside scheduler, because of missing possibility to configure
If you try to use the new swiftmailer spool feature by e.g.
MAIL => ['transport_spool_type' => 'file']
it's currently not possible to trigger the sending by adding a task to the TYPO3 scheduler, because of SendMailCommand uses options instead of attributes for configuration.
Because of this, no configuration is possible there.
The only way to adjust the maximum number of messages to send (message-limit), the time limit for sending messages in seconds (time-limit) and the timeout for recovering messages that have taken too long to send in seconds (recover-timeout) for one call is currently to add an extra cron job.