You can send 6400 mails in a day on one domain. If you have 15 domains, you can send 100,000 mails in one day with little efforts. If you can install script and if you are not a big player, you can save $10 onwards by following trick. Trick : There are several free scripts which have memberships. You can send mails to members. Install script. You have one list ready. My webhost allow 500 mails per hour. I insert 400 emails into one such list. You can increase the list to 16 (as you can send mails for 16 hours). So I can send 6400 emails in 16 hours. If you have more domains, you can send more mails daily. (If you know cron well, you can do better). Of course, this will take some of your time that I know. But its just copy paste and a click on send. This do not take more than 30 secs. This way by little efforts, you can save $25 or more if your list is bigger and you are ready to take efforts or spend money if you are big player.