Posting from discussion thread on GH: https://github.com/mautic/mautic/issues/6451
Basically sending through a mail queue makes a whole lotta sense. Unfortunately, this also delays emails that should better go out immediately like for example double opt-in emails. Especially when offering lead magnets like free ebook downloads or similar stuff people are waiting for the confirmation email to get to their downloads as quickly as possible.
It would be good to have an option for some emails to go out immediately instead of waiting in the queue until the next cron run.