> Now they stop getting followup guidance emails for the course.

This might be the ex-marketer coming out in me, but surely the course guidance emails could be considered transactional to the service and be honoured by a different opt-in/out policy to the newsletter?

> I need to tell every buyer that their account is moving

Again, this use case isn't marketing, and should very much be allowed as a requirement to keep people informed about the use of their data. In the same way a "change password" email is allowed to be sent.

But my email platform doesn’t do that. When you hit “unsub all” you unsub all

That’s the tricky part that most “ew email is spam” folk forget. The definition of “all” can be super nuanced and most people don’t think about it.

From the sidelines, I'd think the answer is that your email platform should have that feature, or you should consider using entirely separate flows/tools for transactional emails and marketing emails. Not a lawyer, but AFAIK transactional emails are not subject to Spam rules & don't even need to have an "Unsubscribe" link. Mixing the two is just causing yourself needless pain.

> From the sidelines, I'd think the answer is that your email platform should have that feature

It does. But the user clicked "No I want to unsubscribe all"

Can you rephrase the choices?

- Unsub from this marketing topic.

- Unsub from all marketing mails. You will continue to receive paid course content; to terminate see [account deletion request page].

On the account deletion page, make it clear that they'll lose out on further paid content, don't come back crying, blah blah.

When in doubt, they're opted out.

Do you really want to open yourself up to being banned by your new platform, or facing a lawsuit over pennies in revenue?

They purchased lifetime access to the content. Should I not give it to them just because they didn’t like an email once?

Imagine being grumpy at a Starbucks barista once and now you can’t get Starbucks again ever anywhere.

Or a better example: You opted out of email now you can’t reset your password. Sorry can’t email you the link.

Why would unsubscribing from your newsletter stop them from accessing the content? Is the content only delivered via the newsletter from which they unsubscribed?

> A while later /../ migrate to a new platform. I need to tell every buyer that their account is moving. But some have unsubscribed from all emails.

They unsub'd all meaning "no more emails ever" as you said. How do I tell them the stuff moved if they don't want to be contacted ever again ever?

You don't have to. When they can't find you, assuming they miss your content, they'll use this miracle tool called a "search engine" to find you.