Mandrill vs Postmark vs SparkPost

Of course we chose Coresender to send our own transactional emails :) So I thought I'll let you know how we use it.

• We set up separate sending accounts for all company needs, eg. transactional emails, monitoring alerts, time to inbox. We even configured our office printers to send emails through Coresender.

• We have a real-time and extremely usable view into what emails go through each account, so each time anybody reports an email not arriving we're able to assist them in a few seconds

• We utilize our message timeline feature, so we can learn eg. if people are clicking on password reset links

• We always know how many of our onboarding emails are being opened which helps us improve them

• Finally, we have full controll over our suppressions lists, so we can add (and remove!) from them whenever necessary.

To sum up, at Coresender we're eating our own dogfood and it helps us stay connected to the product and understand our customers better.

We did a quick test on the reliability of these three common email services, sending a few emails an hour at random intervals.

Unfortunately, none of them had 100% availability over the 30 day test. I don't understand why this is so hard?

Mailgun performed the best with the most reliability and fastest response times. Mandrill was notably bad.

For transactional emails, notifications, reminders, etc, I want to make it so writers/designers can set up the emails and maintain them, and then dynamically insert fields, that I then replace when actually sending the mail from code.

I think the ability to use a basic layout template across individual email templates would make things a lot easier (think header, footer, standard typography, etc).

What is best for this? Why would you prefer Mailgun, SendGrid, Mandrill or something else?