Some other esp's just allow you to send through SMTP without having to create a campaign first, and just require the Hostname, port number, username/password, and the message details, IE sendgrid
https://docs.sendgrid.com/for-developers/sending-email/getting-started-smtp
The Maropost SMTP transactional feature requires a tx campaign to be created and hooked into in order to send emails through Maropost, which is somewhat restrictive. We also require custom headers where we include the required campaign name and auth_token API key.
Would it be possible to align more with that use case where we don't need a TX campaign to be created first and/or the removal of required custom headers and just use username/password to send the API key?
