Email service providers comparison

What is an ESP?

If you are building a SaaS, you need to send emails to users. It is generally not a good idea for you to build out SMTP rails from first principles, which is where the concept of an "email service provider" comes in.

This is a distinct product + infrastructure from "email providers" writ large like Mailchimp or Substack or Klaviyo. Those companies provide email marketing service. (Notably, two providers listed below — Mailchimp and Brevo — provide both email marketing and transactional email services, but we are only listing their transactional email services here.)

Okay, gimme the deets.

Plus some caveats and miscellany:

• SES has a free tier of 62000 emails/month if you're calling from EC2.
• Mailjet does not have sticker pricing for one million emails (thus the lack of data point.)
• As you might expect from a piece of software that is largely commoditized infrastructure that benefits from economies of scale, there are a lot of roll-ups in this space. Mailjet and Mailgun are technically owned by the same parent company; Postmark is now owned by ActiveCampaign, which is a competitor to Mailchimp.

Why should I trust you?

I have no relationship with any of the organizations listed besides being an active customer of four of them (Postmark, SendGrid, Mailgun, and SES), and do not receive an affiliate cut from any of the services mentioned. I have personally integrated with each provider listed below, and have used them to power Buttondown, a newsletter service that sends millions of emails every month.

So uh, does that mean I shouldn't just go with SES?

Well, yes and no. SES is certainly the best-priced option for most use cases, but the developer experience is... not great. The admin tooling is on par with the rest of AWS's dashboard, which is to say it is an acquired taste. If you're sending less than 100k emails/month, I'd personally recommend using another provider whose tooling is more user-friendly; the $10 you save per month is not worth the time you'll spend having to wire up all the things you need.

What's the deal with this 'dedicated IP' thing?

Let's pretend that every single email in the world has a "quality score" associated with it. The higher that quality score, the more likely it is to be delivered to the inbox and avoid the spam folder. One of the many, many factors that goes into that quality score is the IP address that the email is sent from. IP addresses that have been associated with low-quality emails in the past are more likely to be associated with low-quality emails in the future, and so a 'low quality' IP address is going to hurt your quality score.

All ESPs have two options for sending email: shared IP where you're sending mail from a pool of IPs that are shared with other customers, and dedicated IP where you're sending mail from one or more IP addresses that is only used by you.

You might read those two paragraphs as "okay, so I want a dedicated IP no matter what." But that's not necessarily the case. If you're sending a small volume of email, you're probably better off using a shared IP; an IP address with low or spiky volume is going to be associated with low quality.

Do all shared IPs have the same reputation?

Bluntly – no. Some shared IPs are better than others. ESPs have one main lever to keep their shared IPs in good standing with the email providers: they can kick off customers who are sending volume that is driving down their IP address's quality score. The absolute best shared IPs are ones that are the most stringent about kicking off customers who are sending low-quality email. In my (anecdotal, unscientific) experience, Postmark has the best shared IPs and AWS has the worst.

(Again, this only really applies if you're sending a small volume of email. These particulars are less important if your sending volume warrants a dedicated IP.)

I'm sending more than a million emails every month.

You're likely in a position to negotiate a better deal than sticker rate for your volume!

I thought Postmark can only be used for transactional stuff?

That was true in the past, but they've since changed their policy. You can now use Postmark for marketing emails.

Are there any open source options?

You've got a couple options for open source email services:

• Postal is completely free and open source.
• Plunk (mentioned above) is also open source, and offers a self-hosted version.

I can't decide. Tell me who to use.

Okay, fine. Use Postmark. I think their interface is the best.

What about [other provider]?

A couple other folks:

1. Sendune is a wrapper that lets you integrate with AWS SES directly. I have not included them in the table because the backing provider is still SES.

If there's any providers we've missed, please email us and we'll add them to the table.

Gee, it sure is awfully nice of you to compile this resource and keep it up to date. What can I ever do to thank you?

Tell your friends about Buttondown, the best way to add email subscriptions to your newsletter.