What are transactional email service providers?

Transactional emails are user specific emails (usually 1 recipient) that applications send in response to the user doing something: for example, an order confirmation, password reset, or notification email.

In contrast to bulk email, your users usually want to receive their transactional emails (indeed, they could contain the details of something they've just bought: an online voucher code, for example) so it's crucial to treat transactional emails separate from your bulk, marketing emails.

In order to ensure delivery of these emails, it is recommended to use a 3rd party email service provider specically designed to support transactional email delivery.

In this article we review some of the popular transactional email service providers so that you can pick the right service for your use case.

The Services

Before we go through each service in detail let's take a look at the best provider for each category:

• Overall Winner - Postmark
• For Side Projects - Twilio SendGrid
• Cheapest at Scale - Amazon SES

Criteria for Comparison

As an email testing service, and as a team who have built transactional email flows many times, we're in a pretty good position to comment on the quality of these providers.

When we're deciding for ourselves we consider:

• Email Deliverability - How likely is it that the emails get delivered to our users? Does the service provide features to make that more likely like dedicated IPs?
• Tools for Support - How easy is it to support your users when their email go wrong?
• Product Features - Do they support all of the features you would expect?
• Portability - How easy would it be to migrate to a different email service provider should the need arise?
• Pricing - Do they offer a sensible pricing option given the scale of our service?
• Maturity - Does the product have good documentation? Do they provide SLAs? Are their data protection policies good?

The Providers

All of our featured providers provide the following features (which we think are key) as standard:

• API access
• SMTP for sending
• Webhooks for responding to delivery
• Inbound email for processing emails sent TO you
• Bounce handling
• Templating for email content

Postmark

Postmark is a great service for sending both transactional and marketing emails and has the feeling of a very polished product.

Deliverability is great, even without a dedicated IP address, and it's very simple to dig down in to the activity going on in your account.

The only possible downside is that cheaper options are available once you start hitting high email volumes.

Amazon SES

Amazon SES is part of the Amazon Web Services cloud and provides a very mature email sending platform that's designed to handle massive scale.

Being part of AWS is both a blessing and a curse as some of the tools feel a little clunky. For example, implementing web hooks or handling bounces programmatically require use of Amazon SNS which is much less simple than the Postmark equivalent.

Similarly, (and where we're interested) the functionality available for testing email flows is a little clunky with the use of their mailbox simulator.

The major positive though is the pricing. Free to get started, if you're using Amazon EC2 for your compute, and very cheap otherwise.

Twilio SendGrid

Twilio SendGrid is the email API from Twilio, designed as part of their extensive communications platform. On a par with Postmark in terms of functionality and modern design.

They provide a free tier to get started (with 100 emails a day) and then offer pretty competitive pricing, slightly more than Postmark at low volume but then cheaper at a higher volume and provide a dedicated IP address as standard in the Pro tier.

Notable Mentions

Mailgun

Mailgun is part of the Sinch family of products and provides a very competitive product for transactional email delivery.

Pricing is similar to Postmark at scale but they lack cheaper tiers lower down as you're getting started.

Mandrill

Mandrill used to be our provider of choice but, having been acquired by Mailchimp, product development seems to have slowed (almost halted). Now, marketed as an add-on to Mailchimp's core product.

SendInBlue

If you don't mind them putting a "Sent by sendinblue" at the bottom of your emails they provide a generous free tier (of 300 emails a day) to get you going. Quite pricey to get going otherwise.

MailerSend

Great for indie developers wanting to send emails for free but not too bothered about parsing inbound emails. 12,000 emails a month for free.

Azure Communication Services

As an Azure user, it's always seemed odd to use that Azure, for so long, did not provide any way of sending transactional email (to compete with Amazon SES at least).

They've finally delivered their transactional email service as part of Azure Communication Services. If you're on Azure already, it's a great option to simplify your billing but, right now, it's lacking in terms of lots of features. One to keep an eye on!

To find out more, and to see a demo, visit our website