Second reminder sent after the email address was added to blacklist

[shornuk]

We've had scenario recently, where

1. Someone has received the first reminder email.
2. They emailed us to be removed
3. We added them to the blacklist
4. Second reminder was then sent

I can see that the blacklist is only checked at the point of getting abandoned orders. Am I right in thinking that the reminders are both queued at the point of finding the abandoned order? Ideally if it could check again at the point of send that would cover it. Happy to start a PR for it, but would be good to know the way you'd want to implement it.

[mediabeastnz]

A PR would be awesome as this would probably require a decent changer to how the jobs are scheduled.
They both get scheduled currently at the same time with different delays. For this to work you'd either want to find the queued job and cancel it (not easy) or on schedule the 2nd once the first one has been sent (probably a better idea now that I think about it).

[mediabeastnz]

A solution to this should also fix issue #17