The transactional email API space has shifted noticeably in the past year. SendGrid killed its permanent free tier in May 2025. Mailgun doubled pay-as-you-go rates overnight in December 2025. Resend — the youngest of the three — continued gaining ground among developers building on modern JavaScript stacks. If you last evaluated these providers more than twelve months ago, your mental model is probably out of date.
This comparison focuses on three questions: What does each provider actually cost at different scales? Where does the developer experience differ in ways that matter day-to-day? And what should make you choose one over another, rather than treating all three as interchangeable SMTP wrappers?
Pricing: The Landscape Has Changed
All three services price primarily by email volume, but the free-tier situation has diverged sharply.
SendGrid (owned by Twilio) ended its legacy free-forever plan in May 2025. New accounts get a 60-day trial at 100 emails per day, then must upgrade to a paid Email API plan. As of mid-2026, the entry paid tier (Essentials) starts around $19.95/month for up to 100,000 emails; the Pro tier, which includes dedicated IPs and subuser management, starts around $89.95/month. Note that Email API billing and Marketing Campaigns billing are separate tracks — teams that need both pay for both independently, which surprises a lot of people on their first invoice.
Mailgun retains a free tier, but it is genuinely limited: 100 emails per day, one sending domain, one day of log retention, and ticket-only support. Think of it as a sandbox, not a production option. Paid plans step up from roughly $15/month (10,000 emails, no daily cap) through $35/month (50,000 emails, template builder, five-day log retention) to $90/month (100,000 emails, dedicated IPs, 30-day log retention). Overage pricing per 1,000 emails varies by tier — check current rates before committing, since Mailgun adjusted them in late 2025.
Resend offers the most generous free tier today: 3,000 emails per month with a 100-per-day cap, on one domain. Paid plans start around $20/month for higher limits and additional domains. Like SendGrid, Resend separates transactional and marketing email billing — if you want to send broadcast campaigns, that is a separate subscription on top of the transactional plan.
Pricing on all three services has changed multiple times in the last 18 months. The figures above reflect publicly available information as of May 2026 — verify current numbers on each provider's pricing page before signing a contract or projecting costs.
Developer Experience: Where the Differences Are Real
All three offer RESTful APIs and language SDKs. The divergence is in how much friction you encounter between "I want to send an email" and "email is sent."
Resend has the sharpest onboarding of the three. The API surface is essentially one endpoint. The TypeScript SDK ships with end-to-end types that give you proper IDE autocomplete. Its standout feature is first-class integration with React Email — an open-source library that lets you write email templates as React components, rendering them server-side before sending. If you are already building in React or Next.js, this removes the usual pain of wrestling with table-based HTML and inline CSS. Resend added inbound email processing (its most-requested feature) in 2025, so it now covers the full send-and-receive workflow.
One concrete limitation: Resend does not offer native SMTP relay. It assumes you will integrate via HTTP API. If you maintain older infrastructure — a Rails app from 2014, a WordPress installation, a Python script from three jobs ago — that assumption breaks the migration path. You either refactor to HTTP or pick a different provider.
Mailgun is the most technically granular of the three. Its inbound routing lets you define regex or JSONPath-based parsing rules that extract structured data from incoming emails and push it to your webhooks as JSON — useful for building things like support ticket ingestion or order confirmation parsing. The API documentation is thorough, and the dashboard, while not polished, exposes the controls you actually need. Mailgun also offers a choice of US or EU data regions at account creation, which matters if you are operating under GDPR and want email data stored in Europe. That region selection is fixed at signup; migrating a live account between regions causes service disruption, so choose deliberately.
If your application is subject to GDPR and you need email data stored in the EU, Mailgun is currently the most straightforward option among these three. Select the EU region during account creation — you cannot change it later without downtime.
SendGrid carries the weight of being the oldest and most widely adopted of the group. Its compliance tooling — DKIM, SPF, and DMARC configuration, dedicated IP warm-up workflows, reputation monitoring — is mature and well-documented. The breadth of third-party integrations (Salesforce, Segment, Zapier) reflects years of ecosystem development. The tradeoff is that the dashboard feels dated compared to newer entrants, feature releases move slowly, and the split between Email API and Marketing Campaigns billing adds operational overhead.
SendGrid also still supports SMTP relay, making it the practical choice if you are routing email from legacy applications that cannot easily switch to HTTP calls.
Deliverability and Infrastructure
All three providers maintain the technical infrastructure required for solid transactional deliverability: dedicated IP options, shared pools for lower-volume senders, and the standard authentication stack. Claims of exact delivery rates are hard to verify independently — any provider can cite favorable internal metrics — so treat vendor-published percentages with appropriate skepticism.
What you can evaluate concretely: dedicated IPs become available at different price points on each service, and warming up a dedicated IP correctly matters regardless of which provider you choose. On shared IPs (what you use on free and entry paid tiers), your deliverability is partly a function of your sending domain's reputation and partly a function of other senders on the same pool. The three providers manage their shared pools differently, but none publish granular data on how they screen senders on those pools.
Resend's infrastructure is newer and has a smaller customer base than the other two, which means less battle-tested scale but also potentially higher-quality shared IP pools (fewer bad actors, assuming their onboarding screening is effective). This is a reasonable inference, not a verified fact.
Which One to Pick
Use Resend if you are starting a new project on a modern JavaScript stack and want the fastest path from "no email" to "working email with React templates." The free tier is the most usable of the three for actual development, and the API design is the cleanest.
Use Mailgun if EU data residency matters for compliance, if you need sophisticated inbound email routing, or if you are sending volumes where Mailgun's tiered pricing is more favorable than the alternatives. Budget for a proper evaluation of log retention limits — the free and Basic tiers are tight on this front.
Use SendGrid if you need SMTP relay for a legacy application that cannot easily switch to HTTP, if your organization already has SendGrid in its infrastructure stack and migration costs outweigh any alternative benefits, or if you are at enterprise scale where Twilio's support and compliance track record have material value.
For most developers shipping a SaaS product today, Resend's developer experience advantages are real and the free tier is genuinely useful. But "best developer experience" is not the same as "best for every situation," and the pricing gap narrows quickly once you need dedicated IPs or high volume.
Originally published at pickuma.com. Subscribe to the RSS or follow @pickuma.bsky.social for new reviews.
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