Resend vs SendGrid vs Mailgun vs Postmark vs SES vs Loops — which one to actually pick.
The honest operator comparison nobody else writes. Vendor pages can't be honest about competitors. Aggregator pages can't be honest about their ad sponsors. This page ranks the 6 by use case, names where each one breaks, and gives you the math on real monthly cost — not the "starts at $0" marketing line.
For new builds: Resend. Best DX in the category, sane defaults, $20/mo for 50K. For transactional reliability obsession: Postmark ($15/mo for 10K, separate IPs for transactional). For pure cost at high volume: AWS SES ($0.10/1000 — but you eat the ops). For marketing-flow heavy product-led companies: Loops ($49/mo for 5K contacts). SendGrid is hard to recommend for new deployments — Mailgun is niche.
1Forced ranking by overall fit (most builds, most cases)
Resend
The cleanest email API SDK shipped in the last 5 years. React Email integration means your devs write JSX, not HTML strings. Webhook UX is sane. Dashboard doesn't feel like 2014. Native fetch SDK works in Cloudflare Workers with zero adaptation — SES requires the AWS SDK which adds 200KB+ to your Worker bundle. Catch: youngest in the category, so the deliverability track record is shorter than Postmark.
Postmark
Built their reputation on transactional-only delivery. Separate sending IPs for transactional vs marketing means inbox placement on password resets + receipts beats every general-purpose competitor. Slightly more expensive per email but worth it when a delayed 2FA code = a churned user. Also the best support team in the category.
AWS SES
$0.10 per 1,000 emails is 5-20x cheaper than every alternative at high volume. The catch: you handle bounce/complaint webhooks, IP warmup, suppression lists, and sender reputation yourself. For a 1M+ email/mo operator with infra engineers, SES wins by a mile. For everyone else, the engineering hours wipe out the savings. Rule: if you can't name your bounce-rate threshold off the top of your head, you're not ready for SES.
Loops
Built around the modern product-led growth playbook — onboarding sequences, behavioral triggers, audience segments based on product events. Not a transactional-first tool (use Resend or Postmark for that). Pairs well as the marketing layer on top of Resend or Postmark — most PLG startups end up running both.
SendGrid
Now Twilio SendGrid. Feels like 2015-era email infrastructure — dated dashboard, verbose SDK, weaker marketing-side than Loops. Pricing is competitive on paper ($19.95/mo Essentials for 50K) but the DX gap to Resend is enormous. Only pick if you're already standardized on it and migration cost exceeds platform cost.
Mailgun
Strength was always inbound email parsing + EU data residency. Transactional sending is fine but not differentiated. More expensive per volume than Resend or SendGrid. If you specifically need inbound email-to-webhook or European data residency, Mailgun stays in the running. Otherwise Resend or Postmark wins.
2Pick by stack + use case
| Your situation | Pick | Why |
|---|---|---|
| Dev-only transactional · password resets, 2FA, receipts | Postmark or Resend | Postmark if reliability is non-negotiable. Resend if DX speed matters more than the small deliverability gap. |
| Startup with marketing emails too | Resend + Loops | Resend for transactional, Loops for lifecycle/marketing flows. Don't try to do marketing in Resend (yet) or transactional in Loops. |
| High-volume B2C · 1M+ emails/mo | AWS SES | Cost crossover usually hits around 200K-500K emails/mo. By 1M+, SES is the only economic answer — assuming you have ops capacity. |
| Cloudflare Worker stack | Resend | Native fetch-based SDK, zero adaptation needed. SideGuy's own send-email Worker is 80 lines, deployed in an afternoon. |
| Regulated industry · HIPAA, SOC 2, FedRAMP | SES or Postmark | SES has the BAA + most certifications via AWS. Postmark has BAA on Enterprise tier. SendGrid has BAA but the rest of the platform isn't worth the trade. |
| Need inbound email-to-webhook | Mailgun or Postmark | Both have solid inbound parsing. Resend doesn't ship inbound at all. SES inbound exists but is painful. |
| EU data residency required | Mailgun or Postmark EU | Both offer EU-hosted regions. Resend is US-only as of this writing. |
3Where each one breaks
Resend
Youngest deliverability track record + US-only regions. Deliverability is genuinely good but doesn't have 10 years of receipts like Postmark or SendGrid. No EU residency yet. No native marketing-email layer (you bolt on Loops or roll your own). For most new builds these are fine; for regulated/EU/marketing-heavy they're real gaps.
Postmark
Premium pricing per email + slower SDK iteration. Costs more per send than Resend or SendGrid on equivalent tiers. SDK is solid but doesn't get the React Email-style modernization that Resend ships. Don't try to use Postmark for high-volume marketing — it'll work, but you'll overpay.
AWS SES
Ops tax is invisible until your sender reputation tanks. SES gives you raw infrastructure — you handle the bounce loop, the suppression list, the IP warmup, the SPF/DKIM/DMARC setup, the dashboard you build yourself. First time your bounce rate spikes and AWS pauses your account is when teams discover what they signed up for. Mitigation: only pick SES if you have an infra engineer who already gets this.
Loops
Not a transactional-first tool. Don't try to make Loops your password-reset or receipt sender. The deliverability profile and SDK ergonomics are tuned for marketing/lifecycle, not transactional reliability. Use Loops for what it's good at; use Resend or Postmark for the rest.
SendGrid
DX is stuck in 2015 + Twilio acquisition slowed product velocity. Dashboard feels dated, SDK is verbose, support has degraded post-acquisition. Marketing email side (Marketing Campaigns) is weaker than Loops or Customer.io. The platform works — it's just no longer the obvious pick for anything specific.
Mailgun
Generalist tool in a category that rewards specialists. Outside of inbound parsing + EU residency, every alternative does the core sending job better, cheaper, or with better DX. The 2017 Rackspace divestiture started a long product-velocity decline they haven't recovered from.
4FAQ — operator-honest answers
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I run SideGuy out of Encinitas. No retainer, no demo call. Send a 1-line description of your stack + send volume, get back a forced recommendation in plain English.