This is a port of Postmark.js (https://github.com/voodootikigod/postmark.js) for Meteor. Only works on server (I think PostmarkApp blocks the client). Here is basic usage:
Postmark("YOUR_API_KEY").send({ From: "Test <test@example.com>", To: "foo@bar.com", Subject: "Test", TextBody: "Hullo!" }, function (err, res) { console.log(err, res); });