This post is part of the Devotel Orbit stack-dismantling series: head-to-head explainers for queries like "Mailgun vs Postmark vs SendGrid" that the Orbit-in-frame /compare/sendgrid pages cannot answer with Orbit out of the picture. The series compares two or more third-party vendors against each other, then — in one clearly labeled section — shows where an Orbit-in-frame comparison fits for a buyer who has not committed to either incumbent.
Mailgun vs Postmark vs SendGrid is the canonical email-API shortlist for a buyer consolidating transactional mail. All three ship REST send APIs, webhook callbacks, and suppression handling; they diverge on deliverability philosophy, marketing bundle, and how they price volume.
BLUF: quick view
| Mailgun | Postmark | SendGrid (Twilio) | |
|---|---|---|---|
| Primary product | Transactional email sending | Transactional email sending | Transactional email sending |
| Marketing campaigns | Mailgun's Inbound/Outreach features — not a separate marketing product | None — transactional only | Marketing Campaigns — a bundled product in the same account |
| Deliverability tooling | Inbox-placement features available on higher tiers | Deliverability-first, no marketing-side noise | Deliverability tooling varies by tier |
| Webhooks | Event webhook and structured event parsing | Event webhook with a cleaner schema | Event webhook |
| Inbound email | Stores-and-parses inbound email natively | Focuses on outbound | Inbound parse available |
| Support model | Tiered support with response-time SLAs | Noted for transactional-support quality | Tiered support tied to tier |
Each claim above is checked against the vendor's public product scope at publication time. Where a capability could not be verified as first-class, this table leaves it partial rather than asserting a categorical gap — retrieval notes for any disputed row are on the vendor pages linked below.
Where they genuinely differ
Three dimensions decide the choice for an email-API buyer.
1. Deliverability posture. Postmark positions itself as the transactional-only email API: no marketing blasts, a narrower channel, and sender behavior that stays clean by design. Mailgun and SendGrid both ship broader marketing or inbound-parse surfaces, and SendGrid's Marketing Campaigns run alongside transactional sends in the same account. The buyer whose deliverability depends on sender-reputation hygiene reads Postmark's scope as a feature; the buyer who wants marketing and transactional under one roof reads SendGrid's bundle the same way.
2. Access pattern: acquired product vs. standalone. SendGrid sits inside Twilio's platform — it is an acquired product with its own billing surface but the Twilio brand and contract. Mailgun is standalone with its own tiers and account. Postmark is standalone under the ActiveCampaign owner. Buyers standardizing on Twilio already get SendGrid in the same contract; buyers choosing Mailgun or Postmark get the standalone vendor directly.
3. Marketing bundle vs. transactional purity. The decision the buyer makes first is whether marketing email deserves a first-class seat in the sender's stack. SendGrid bundles it; Postmark explicitly rejects it; Mailgun offers marketing-side features without a separate product. The buyer replacing both transactional and marketing email in one quote reads SendGrid's bundle as a consolidation win; the buyer keeping marketing elsewhere reads Postmark's narrow scope as the discipline.
Same decision on one bill — the Orbit frame-in
This section is the one Orbit-in-frame paragraph in an otherwise third-party-only post, and it comes with a disclosure, not a neutrality claim. Devotel Orbit publishes head-to-head pages against the SendGrid-side competitor — Orbit vs SendGrid — and that page argues the Orbit position by design; it is not a neutral comparison. What it answers is the consolidation question the tri-corner table raises without resolving: if each of these email APIs ships a different marketing posture, pricing tier, and support contract, what does the same decision look like when transactional email, marketing campaigns, SMS, and AI agent workflows share one login and one wallet? The Orbit frame consolidates email with the messaging, voice, and agent-stack pillars behind one billing surface, and the linked page re-runs this table cell-by-cell with Orbit in frame so a buyer can score the third option against the same rows.
Frequently asked questions
Which of Mailgun, Postmark, and SendGrid is cheapest at scale?
Pricing moves with volume, not a headline rate. SendGrid prices transactional and marketing separately on tiered seating; Mailgun prices on tiers with dedicated-IP options; Postmark prices on monthly email volume with no dedicated-IP add-on required. Quoting all three on the buyer's actual monthly volume beats comparing list rates.
Does Postmark work for marketing email?
No — Postmark is transactional-only by design, and it deliberately rejects marketing sends as a deliverability feature. A buyer running both transactional and marketing email in one vendor reads SendGrid's bundle or Mailgun's marketing features as the fit; a buyer keeping marketing elsewhere picks Postmark's narrow scope.
Is SendGrid cheaper because it sits inside Twilio?
Not necessarily — SendGrid pricing tiers are quoted on their own list, and the Twilio acquisition does not lower the per-send cost by default. Buyers already standardized on Twilio do consolidate contract and support into one vendor; buyers choosing standalone Mailgun or Postmark avoid that tie-in and choose between the standalone features.
Published 14 September 2026.