First and formost, there's a bit of an "apples vs. oranges vs bananas" comparison here. We need to start by drawing a line between email sending engines and email deliverability engines. Then, we'll draw a line between the delivery of transactional email (that your webapp sends) and bulk email (your marketing campaigns).
While Postmark's price per 1000 sends is "higher" than some of our competition, we provide our customers with access to the full deliverability & diagnosis stack that we provide for our accounts regardless of how much they spend monthly. Also, our price per 1000 sends drops to $1.00 for bulk credit purchases starting at 500k credits, $0.75 for 1MM+, and $0.50 for 2MM+.
When you compare Sendgrid (along with SES, Mailgun, etc), you need to look at what we each offer at each price point.
In Tim Falls' answer on Quora, he says:
>"If you want the best possible feature set we have to offer, which includes a dedicated IP, our entire suite of APIs, an exhaustive collection of stats and more, you can sign up for our Silver plan or higher - Silver gets you 100k emails/month for $79.95, and everything we have to offer.
> In conclusion: yes, our Lite plan is similar to SES and is very basic in terms of features - which could put it in the "commodity" category. However, at higher price points, you can get everything you need to operate a fully functional email system - without the hassle of doing everything yourself and with access to our team of experts, who are available by phone, live chat, and email."
Tim's right. SES is very basic and is in the commodity category. It's an email sending engine, NOT a deliverability engine.
Tim also points out that in order to get what they consider "a fully functional email system", Sendgrid customers need to spend at least $80/month.
Postmark is $1.50/thousand (or less) with no minimums. You can literally spend $1.50/month with us and get the same level/quality of service as someone spending thousands of dollars/month with us.
In addition to our specialized delivery infrastructure, and the tools we provide that can help you with self-diagnosis of delivery issues, our team has over 7 years of email delivery experience and has an extremely strong track record for pinning oddball delivery problems that arise even with best-of-breed delivery infrastructure. Our customer service isn't just fanatical and friendly, they're experienced in the problems you're likely to have.
How does this "transactional vs. bulk" mail conversation affect you bottom line?
Sending an important transactional email from the same infrastructure as your marketing email queue increases the likelihood that your transactional emails will be throttled as if they were part of a bulk campaign. A missing or slow-to-deliver "forgot password" email, for instance, could be the loss of a customer to a competitor while they can't get into their account, which obviously affects your bottom line. Further, transactional email gets read, which means if you're going to put "marketing" in an email, it has much more value in a transactional email because it's more likely to be read (with the caveat, of course, that it's done tastefully).
So in addition to our low tolerance, we also strictly prohibit bulk/marketing email sending on Postmarks infrastructure to keep our reputation for transactional emails as high as possible. Our laser focus on a specific email delivery category keeps our delivery rates as high as possible for customers who abide by our sending guidelines, and that premium informs our price point as well.
And how do we know all this?
We ran an email marketing service for 7 years and learned a lot about what works and what doesn't. We ALSO run one of the most popular SVN/Git/Mercurial hosting services - Beanstalk. Beanstalk sends significant volume every single day, and was one of Postmark's first "customers". And when we have ZERO deliverability problems ourselves, we have huge confidence in our ability to provide that to others by following our own guidelines. And it's not just our own apps - we've had people come to Postmark after being dissatisfied with others' deliverability rates, and have been pleased with Postmark's performance.
[1] http://www.quora.com/Why-are-Mailgun-and-Postmark-so-much-mo...