Yep, and I'm also talking about human spam complaints. Small numbers of forgetful people -- people who forgot they opted-in -- won't impact your reputation. A gigantic leap in people reporting your emails as spam, even if they are objectively incorrect, will be very bad.
I can see that. I guess I should have prefaced this by saying that these email addresses are already in our database and receive email communication from their utility company regularly, whom we send on behalf of for certain items. So this is a B2C email send. These emails come from a separate ESP (SendGrid), but we needed to utilize a token functionality which we can do from Marketo. So we're simply sending from a different ESP to a list of people we already send to.
OK, if they're all accustomed to receiving emails from your same domain, with the same domain referenced in the body, then I'd be less worried about the human factor mentioned above.
But Greg's points about automatic spam/hammering detection still stand, for sure.
I think I'm going to break the batches up and send ~10,000 per hour over two days for the first 80,000. And then do the same for the next 80,000. I'm hoping we don't run into any issues...
If you are on Marketo's regular shared server then I'm not aware of any rules around number of sends. However, if you are on the trusted level of shared server then you are capped at 75,000 email sends in a 30 day period. Deliverability is MUCH better on the trusted level of shared server so before you send I would double check to make sure you are not on that level and subject to the cap.