I work for a charity that is putting on an event next month, a fundraising walk.

The event registration page was originally built with an email unsubscribe checkbox. People who checked this box got flagged in our back end as "do not ever email", i.e., unsubscribe is global.

Approximately 150 people checked this box. This means that not only do they not receive emails from us in general (which is OK, that is what unsubscribe does), they do not receive emails about the event (not OK - they are not going to get info about things like directions, parking, day-of-event instructions, etc.)

The original unsubscribe language was very general, so there is a good possibility that unsubscribers did not know they were unsubscribing from all our emails, even for the event for which they just registered.

The event registration page has since changed so that event registration constitutes a global email opt-in. So I am dealing solely with this group of 150.

I am being asked to email this group of 150 about the event (directions, parking, day-of-event instructions, etc.). We would still respect the general unsubscribe and thus not include these people on our regular email list.

How kosher is this? How would you handle this? First send them an email saying, "We know you unsubscribed, but...?" Could event-related emails to this group be construed as "transactional" and thus be OK to send despite the receivers unsubscribing?