[Solved] Cancel/delete user subscriptions

Hi,
I just had a bit of a panic when I tried sending some emails and my server sent me mail delivery failures with the reason being "exceeded the max defers and failures per hour."
I thought I was hacked or something but it turns out some comments were made to a post with many existing comments and some subscriptions on this post existed, but multiple email addresses were bad or no longer working so my mail server went into protection mode and blocked outgoing email.

Now I understand you offer subscription management in a paid add-on, but I would think it makes sense you let me at least delete subscriptions of users/emails that are no longer valid and cause problems with my email server.

So, is there any way to cancel/delete subscriptions without using the add-on?

Thanks!