Don’t most of these services explicitly disallow using them for newsletter type of use? If you send a bunch of the same types of emails to bursts of thousands of users at once, those companies have algorithms that will eventually pick it up (especially if there are lots of images/content embedded).
Am I misunderstanding the limitations of which services are available to use for “bring your own SMTP”?
Am I misunderstanding the limitations of which services are available to use for “bring your own SMTP”?