The problem here is that they are in-between two distinct needs 1) low volume transactional email 2) high volume (but very intermittent) distribution. Most s

The problem here is that they are in-between two distinct needs 1) low volume transactional email 2) high volume (but very intermittent) distribution. Most service cater to one or the other (and for #2, most cater to non-intermittent use). I would almost say that your best bet here is to roll-your-own SMTP delivery server. It's going to be a pain though because you'll have to delve deeply into email delivery/anti-spam issues (what you pay someone like mailgun or mailchimp to manage for you). If I was doing this and had to do it on the relative cheap, I would probably use SES. When it came time to send that 30,000 recipient email I'd build some sort of queuing system that talked to SES and delivered the email at a lower rate, over several days (say, 10,000/day for 3 days, or something like that). That may seem like an ugly way to do it, but then you do get to take advantage of that $0.10 per thousand (plus bandwidth) price. You could also contact AWS and ask for a higher daily limit, they do specificity state "If you need to send more volume per day than your current sending quota, please contact Amazon Web Services and we will evaluate your request promptly." on the page.