At the end of the day, when a competitor like Amazon enters a market, you reach the bottom. There's no way Postmark or SendGrid or Mailjet or Postage or SocketLabs or SendLabs are going to be able to compete on price.
And I don't think the point is to compete on price, but on features and service. Postmark's roadmap is bristling with awesome. At the end of the day customers win when there's innovation and competition in a market.
To answer your question, Postmark and others have support for SMTP to ease integration with companies already using a stock SMTP implementation. There's also insight into email deliverability, being able to handle DKIM/SPF issues for you, inbound processing, etc. It comes down to your use case, and the merits of the service (actual deliverability rates for example).
does Postmark support multiple custom 'FROM' addresses? In our SaaS app the admin user specifies their FROM e-mail but I know they must be verified by your system. Is there an API for this? If so could the verification e-mail be custom branded?
@Ryan We do support multiple 'FROM' addresses for customers whose business models require it; just email support when you want to enable it, which will circumvent the need for verification.
I've moved away from Amazon SES due to issues with Hotmail/Outlook spam filters. Now using Postmark with none of my messages getting marked as Junk compared to 20% with SES. +1 for Support too in getting Sender Signatures set up. I blogged about it: simplybillapp.tumblr.com/post/76320865336/
@DanielCrenna +1 to you for mentioning Postmark. Was gonna use SendGrid, but I like this much better (on both price and features).
On the subject of price, both SendGrid (lite plan) and Amazon SES charge $0.10 per 1,000 emails.