Transactional email services compared: Brevo, Postmark, Mailgun, SES, SendGrid, Resend, Mailjet, Infomaniak, SMTP2GO

What are transactional email services?

A transactional email service is an SMTP or HTTPS API that reliably delivers individual outgoing messages to Gmail, Outlook, Bluewin or Hostpoint mailboxes. The difference from marketing platforms like Mailchimp is clear: it is about password resets, dunning, invoices, confirmations and audit mails -- individual user-triggered messages that must arrive within seconds.

In a Swiss fiduciary or SME setup, this is the invisible infrastructure behind every login, every onboarding mail and every client dispatch from the accounting tool. If the service fails or lands in spam, the end client perceives this as a fault of the fiduciary software. That is why selection matters, instead of accepting the first default option of the CRM or ERP.

As of May 2026, nine serious options exist on the market. Three are hosted in the EU or Switzerland (Brevo, Mailjet, Infomaniak), five are US-centric with optional EU regions (Postmark, Mailgun, Amazon SES, SendGrid, Resend), and SMTP2GO offers multi-region routing including the EU. The choice depends on three axes: deliverability, data residency, price per 1000 mails.

Why it matters

Three points decide suitability for a Swiss fiduciary: deliverability, data residency, and DKIM/SPF/DMARC setup comfort.

Deliverability: Whoever sends a dunning notice to a client and lands in the spam folder has a collection problem. Postmark leads independent tests (Mailgun Email Tool Tester, Q1 2026) with over 99 percent inbox rate, followed by Brevo and SES at 95-97 percent. Mailgun and SendGrid sit lower, but cheaper per mail. Whoever sends 500 dunning notices sees the difference in cash flow.

Data residency: An invoice mail contains client names, amounts, IBAN hints, tax codes. That is personal data under revFADP and potentially professional secrecy (Art. 321 SCC) when a fiduciary holds the mandate. Whoever sends via Postmark (USA) or SendGrid (USA) transfers this data into a third country and needs a data-transfer impact assessment (see TIA topic). Brevo (France plus Frankfurt), Mailjet (France) and Infomaniak (Geneva) solve this without a TIA.

DKIM/SPF/DMARC: Since February 2024, Google and Yahoo require strict DMARC for senders with more than 5000 mails per day. By May 2026, this is standard, and some mailboxes (notably Microsoft 365) flag mails without DMARC alignment as suspicious. All nine services support DKIM and SPF, the difference lies in setup comfort: Resend and Postmark lead with clear DNS instructions, SES requires manual domain verification per AWS region.

The nine providers in detail

Brevo (France, formerly Sendinblue, EU-GDPR compliant with DPA): Free plan 300 mails/day, Starter from EUR 19/month, hosting in France plus Frankfurt mirroring. Offers combined SMTP and marketing CRM, which is convenient for SMEs. Inbox rate 96-97 percent.

Postmark (USA, Wildbit/ActiveCampaign): Specialist for transactional mail only -- no marketing features, but best deliverability (99 percent plus). From EUR 15/month for 10000 mails, inbound routing included (webhook on incoming mail). Clear dashboards with bounce codes and heatmaps.

Mailgun (USA with EU region Frankfurt): Developer-oriented classic, from EUR 35/month for 50000 mails, strong API with good SDK in 8 languages. Inbox rate 93-95 percent, slightly behind Postmark. With EU region usable for GDPR setups, then with DPA.

Amazon SES (AWS, EU regions Frankfurt/Ireland/Zurich since 2025): Price winner with USD 0.10 per 1000 mails -- roughly 10-30x cheaper than competitors. But no dashboard, no click tracking out of the box, much self-build. Whoever runs an audit platform and collects telemetry anyway wins clearly with SES.

SendGrid (Twilio, USA, EU region available): Market leader with USD 19.95/month for 50000 mails (Essentials). Free tier was sharply cut back in 2026. Inbox rate 92-94 percent. Very broad ecosystem integration (Salesforce, HubSpot, Twilio voice link).

Resend (USA, founded 2023, makers of React Email): Developer-first with TypeScript SDK, clean API, React Email templates. Free 3000 mails/month, Pro from USD 20/month. Pretty onboarding and best DX, but young and without Swiss hosting. Suitable for startups, less for fiduciaries with client confidentiality.

Mailjet (France, subsidiary of Mailgun/Sinch): Sister to Mailgun but with EU-first hosting in France. Free 200 mails/day, Essential from EUR 17/month. DPA available, GDPR-compliant. A convenient choice when the Mailgun API is already known.

Infomaniak Mail Sender (Switzerland, Geneva): CH-DSG compliant, servers in Geneva and Sion. From CHF 0.05 per 1000 mails, coupled with hosting and DNS packages. The only solution with pure Swiss data residency -- ideal for law firms and Swiss fiduciaries with strictest data residency. Inbox rate 92-94 percent, slightly weaker than US specialists, but zero data export.

SMTP2GO (New Zealand with EU and US routing): Free 1000 mails/month, from USD 15/month for 10000 mails. Very clear dashboards, multi-region choice, simple setup. Inbox rate 94-96 percent. A pragmatic alternative when the US providers are too complex and Brevo is too marketing-heavy.

Selection workflow in 6 steps

1. 01Clarify data residency: must client data stay in CH/EU? If yes, US-only options (Resend, SendGrid) without TIA are out.
2. 02Estimate volume: how many mails per month? < 10000: Brevo Starter or Postmark; 10k-100k: Mailgun/SendGrid; > 100k: Amazon SES.
3. 03Check content sensitivity: dunning, invoices, client files or marketing? Verify pseudonymisation in the mail body.
4. 04Try DKIM/SPF/DMARC setup: shortlist 3 providers, 30 minutes test account and DNS setup each. Which works without support ticket?
5. 05Real deliverability test: 50 test mails to Gmail, Outlook, Bluewin, Hostpoint, Sunrise. Count inbox vs spam.
6. 06Check contract and DPA: with EU/CH providers DPA is automatic, with US providers set up and document a TIA.

Recommendation by use case

Swiss fiduciary with professional secrecy and maximum residency: Infomaniak Mail Sender. Servers in Geneva, Swiss DPA contract, same provider as hosting and DNS. Slightly weaker inbox rate but zero data export -- wins the compliance argument clearly.

SME with EU hosting requirement plus marketing needs: Brevo. Free plan of 300 mails/day covers most fiduciary offices, Starter EUR 19 covers 10000 mails monthly. Combines SMTP and newsletter features in one DPA-ready EU contract.

High deliverability for dunning and invoicing: Postmark. When the last mail before collections must arrive, Postmark is the right choice despite US hosting. With TIA and pseudonymised client names in the mail body, compliance holds.

High volume and full control: Amazon SES, EU region Frankfurt or Zurich. Whoever sends 100000 mails per month saves hundreds of francs versus Brevo/Postmark -- but builds bounce handling and dashboards in-house.

Startup or new product on modern code base: Resend. Best developer experience, TypeScript SDK, React Email templates. Ideal for internal tools and MVP phase.

Known API, EU-first: Mailjet. When the Mailgun API is already widespread on the team but the company requires EU hosting, Mailjet is the direct switch.

When these services are wrong

Pure marketing newsletters with segmentation logic and A/B tests belong in a marketing platform (Mailchimp, ActiveCampaign, Klaviyo) -- not in a transactional service. Brevo is the special case: it combines both, but whoever segments more than 10000 recipients should build the marketing path with engagement scoring separately.

For mails that absolutely must never leave Swiss territory (notary, criminal proceedings, sensitive medical and tax files), Brevo is also unsuitable -- only Infomaniak or a self-run Postfix server with local SPF/DKIM meets that bar. Self-run SMTP is feasible but building reputation takes 3-6 months during which many mails go to spam. For smaller offices the effort rarely pays off.

For pure inbound logic (parsing incoming mail, opening tickets), Postmark Inbound and Mailgun Inbound are the only serious options among the nine -- the others cannot do this, or only with limits.

Trade-offs

FAQ

Related topics

Sources

1. EmailToolTester -- Best Transactional Email Services 2026 · 2026-04
2. Brevo Blog -- Best Email API Services 2026 · 2026-03
3. Postmark -- Transactional Email Pricing · 2026-05
4. Amazon SES Pricing (USD 0.10/1000) · 2026-05
5. Resend Pricing 2026 · 2026-04