I'm currently sending emails to the first 50,000 addresses listed in the database dump via SendGrid. I only have 50,000 credits left for this month, but at least that many will get notified.
A bit too late now, but that violates at least the first three terms of the SendGrid e-mail TOS and I wouldn't be surprised if SendGrid got a "bit upset" about it..
Well, haven't actually clicked the send button yet.. was waiting for the import to finish. I'm second-guessing the foolhardy good samaritan effort now, though. ;)
It's a free account that I got via an AppSumo bundle, so no real loss to me if it gets terminated, but I'd rather not go that route to begin with, ya know?