I know you will be able to find the best email service provider for sure but you have yo make sure you spend less on your bulk email Marketing needs. If you a have valid email opt in list then you can use easy sendy pro or binaryclues bulk emailing software which helps you send min. 100k emails a day.
Just make sure the email I'd you have are correct otherwise you domain might get blacklisted. I will share a competitive chart below which will help you take a faster decision.
If the information was helpful, please let me know your response. I will try to assist you to my level best as I have used both of them and both are very good tools for sending millions of emails