By Jordie van Rijn: The only true way to know is to make a list with all ESPs and count each and every one of them. Find all those companies, check if they really have a focus on email marketing services and what they really do. Just by the numbers a daunting task when you think of it. But that didn’t stop us. So without further ado, we give you the actual current number of ESPs. (It is updated every half hour.) Because the number of ESPs fluctuates, you might say it is just like the stock market. New ESPs are started each day and others merge or go out of business just as fast. All the ESPs counted are listed in our total list of ESPs, so take a look there! Currently we have 40 email service providers on our “to be reviewed†list, they aren’t yet included in the count for the total number of ESPs. The List: http://www.emailvendorselection.com/email-service-provider-list/
Def not a complete list but some of these comments are pretty good. MailChimp MailChimp is email service provider with an ape. They are well known for their freemium pricing model.
I was talking to a very, very high-end industry exec on the phone yesterday, and he asked "What ESP do you use, SuperGenii?" just like that. So people are spreading the word.