I’ve tested a bunch of the major players. Below are some quick notes. They’re roughly ordered based on my preference.
Mandrill: I started here and really like it. They got me in the door with 10,000 emails for free a month and it is easy to set up, reliable and the best feature is the simple dashboard that also shows you the content of the email sent, which helps! Their WordPress plugin is the most downloaded of the bunch too and I found it really easy to use. They also allow you to more easily switch the sending email for accounts without having to add a bunch of text records in the DNS which makes it easy if you are sending a bunch transactional messages on behalf of your customers. The least expensive route now is to buy the 0-500 Mailchimp plan even if you don’t use it for mass mailers, then you can buy a block of 25,000 transaction emails for $25. Mandrill’s pages also just load fast — much faster than SendGrid.
Postmark app: I am still demoing this here. It’s, possibly, the most complicated to set up but that also may be because it seems they are the strictest about limiting use of the service to transactional emails which they claim helps them maintain their high reputation and improve deliverability. I love the small Wildbit team in Philadelphia.
Amazon / Sendy: Sendy makes Amazon’s messaging service easier but I am still suspicious of deliverability via Amazon and suspect it’s used by a lot of spammers. It’s cheap though if you are sending hundreds of thousands or millions of emails.
Malgun (by Rackspace): These guys made it easier to set up. They have a cool tagging feature for organizing your mail. Mandrill has this too. And you can see the full content of your mail with them too, which is important.
Sendgrid: I tried this after Mandrill went to a paid model. They offer many features but it’s almost too much. The UI is harder to use, as a result. And they don’t save the content of the email which, I think, is a killer feature! SendGrid’s pages also weren’t loading quickly for me. And I had a problem where the log in cookie wasn’t maintaining my logged in status and kept pushing me out when I’d revisit.
Mailjet: I tried them and left when they had some server issues. They’re also based in France and I prefer Stateside companies, if possible.
Developing … I will update this with better reviews over time. This is just a log for me.