SendGrid vs Mailgun vs Postmark for Transactional Email

Postmark is the strongest pick when transactional email is your priority: it keeps 45 days of message history by default and runs transactional and broadcast mail on separate infrastructure. Mailgun suits developers who want flexible routing, inbound email and a free tier of 100 emails a day. SendGrid fits teams that already use Twilio or want transactional and marketing email under one roof, but it no longer has a permanent free plan.

All three are mature, reliable services, and any of them will deliver an online store's or app's email well when the domain is set up properly. The differences are in price at your volume, how long you can look back at what was sent, how they keep marketing mail from hurting order emails, and what support you get. Figures below are from each provider's own pricing and documentation pages at the time of writing (November 2026), and Worklancio takes no commission from any of them.

#The short answer by situation

If you run a WooCommerce store or a SaaS app and mainly care that receipts, password resets and login codes arrive quickly, start with Postmark. If you are a developer who wants to receive and parse email as well as send it, or wants a free tier for a side project, look at Mailgun. If your company already runs SMS or voice on Twilio, or wants marketing campaigns and transactional email from one vendor, SendGrid keeps things in one place.

For a wider view including Amazon SES, Brevo, Resend and others, see my comparison of transactional email providers.

#Head-to-head table

Pricing pages change often and most providers discount yearly billing, so treat these as a snapshot and open each page before deciding. Postmark's overage rates are $1.80, $1.30 and $1.20 per 1,000 extra emails on Basic, Pro and Platform respectively.

#Deliverability features

All three sign your mail with your own domain once you add their DKIM records, handle bounces and keep suppression lists so you stop emailing dead addresses. The differences are in what they add on top.

Postmark builds its whole product around transactional mail. Its message streams page describes transactional and broadcast email running on "separate, parallel" IPs, so a newsletter complaint does not touch your password resets. Postmark also vets senders by hand and has systems to stop likely spam before it sends, which protects the shared IPs everyone uses.

Mailgun lists suppression management and link tracking, adds send time optimisation and 5,000 email validations on Scale, and sells validation as an add-on on lower plans so you can clean addresses before you send. Inbox placement testing and reputation monitoring sit in its separate Mailgun Optimize product.

SendGrid includes email validation credits on Pro and Premier, dedicated IPs from Pro, and lists IP warm-up among its features. Subusers let you split different apps or clients so their reputations stay apart.

None of these replaces getting the basics right. SPF, DKIM and DMARC on your domain, a clean sender address and no marketing mail on the transactional path matter more than which logo is on the invoice. My guide to domain and business email setup covers those records, and emails going to spam covers what to check when they are in place but mail still lands in junk.

#Message streams and keeping mail types apart

Mixing marketing and transactional email on one sending path is the most common cause of order emails landing in spam. A newsletter gets spam complaints, the shared reputation drops, and receipts suffer.

Postmark makes the split compulsory: each server has transactional and broadcast streams, broadcast mail needs an unsubscribe link, and the two never share IPs. On SendGrid and Mailgun the split is your job. You can send marketing from a separate subdomain, a separate subuser or account, or a separate dedicated IP once your volume justifies one. This works, but it relies on whoever set up the account doing it properly.

For a WooCommerce store, the practical rule is simple: order, shipping and account emails go through one stream or domain; newsletters and abandoned-cart campaigns go through another.

#Log retention and why it matters

Logs answer the question every store owner hears: "I never got my order confirmation." With a log you can see whether the email was delivered, bounced or never sent, and prove it.

Postmark default message history

45 days

Mailgun on the Scale plan

30 days

SendGrid on Pro and Premier

7 days

Mailgun on Free and Basic

1 day

A week of history is enough to debug a broken form. It is often not enough for a customer who notices a missing invoice two weeks later. If you choose SendGrid or a lower Mailgun plan, consider sending events to your own system through webhooks so you keep your own record. All three providers offer event webhooks for deliveries, bounces and complaints.

#Pricing models compared

The three price in slightly different ways:

• SendGrid sells plans by monthly volume and features, starting at $19.95 for Essentials. The pricing page says the exact price depends on volume, and suggests Essentials for 50,000 to 100,000 emails a month.
• Mailgun includes a set volume in each plan: 10,000 on Basic, 50,000 on Foundation and 100,000 on Scale, with Foundation and Scale offering a free first month at the time of writing.
• Postmark starts every paid plan at 10,000 emails and charges per 1,000 above that, with the rate falling on higher plans.

At low volume, Mailgun Basic and Postmark Basic cost the same. As volume grows, compare the exact tier on each provider's calculator, because the cheapest option changes with your monthly count. If cost per email is the main concern at very high volume, Amazon SES is usually cheaper still; my Amazon SES with WordPress guide shows the setup.

#Support

Support differs more than the marketing suggests. Mailgun lists ticket support on its free plan and live phone and chat support on Scale. SendGrid offers personalised support and expert email programme management as paid extras. Postmark's pricing page does not set out support levels by plan, so ask before you sign up if fast human help matters to you. Whichever you choose, keep someone on your side who understands DNS and email headers, because most delivery problems start on your domain, not at the provider.

#How a professional chooses for a client

The choice usually comes down to four questions:

1. How many emails a month now, and on the busiest day of the year?
2. How long do you need to look back at a message's history?
3. Will the same account send marketing email?
4. Who will check bounces and alerts after launch?

A store or app with a clear answer to those can pick in minutes. My SMTP and transactional email setup service covers provider choice, DNS, webhooks and testing. For apps, the email setup is part of my custom web application development work, and for stores it is part of WooCommerce development.