I have a web app where a registered user can create an appointment and then add a list of contacts that they wish to invite to that appointment. These other users are not necessarily registered users of the app.
Upon clicking "confirm", I would ideally like my backend to dispatch invitation emails to each of those invited users on behalf of the inviter.
This seems to me to be a pretty average invitation workflow... but are these kinds of emails generally frowned upon?
I ask because I checked a few email providers like Postmarkapp[1], and they seem to disallow any kind of emailing where the email recipient did not take any action to initiate that particular email transaction.
[1] When I take their quiz that helps to determine whether Postmark is a good fit or not for my usecase, it says the following:
It sounds like Postmark is not a good fit for your sending needs. Postmark requires that messages be fully opted-in—meaning recipients would expect to receive the messages you'd be sending them.
Postmark allows transactional and broadcast emails. According to their own explanation:
Transactional email is typically a unique, high-priority message sent to a single recipient. They are often triggered by something a user does or doesn’t do. Broadcast email, on the other hand, is sent to multiple recipients at once. Things like product update announcements or terms of service notices are examples of broadcast emails.
Your emails may fall into the marketing email category (as your email recipients neither expect nor opted in to receive these emails), which is not supported by Postmark.
Read Postmark's Transactional vs. marketing email blog post for an in-depth explanation.
Here's a non-exhaustive list of providers that permit marketing emails: