Best transactional email services in 2026, compared

A transactional email service sends the messages an application triggers for one recipient at a time (password resets, receipts, verification codes) through infrastructure with an established sending reputation, and reports back what happened to each one. The market moved a lot in the last two years: SendGrid retired its free plan in 2025, SparkPost disappeared into Bird, and several providers repriced. This comparison covers nine services with their current pricing, what each is genuinely good at, and where each falls short.

One disclosure up front: Lettr is our product, so its entry below is the vendor's own case. Every price and test result for the other eight comes from their public pricing pages and named third-party tests, checked in July 2026.

What to compare before the price

The nine services below all do the same basic job: accept a message over a REST API or SMTP relay and deliver it. The differences that matter in production are less visible than the price:

• Traffic separation. Whether transactional mail shares IP pools with marketing blasts. Shared pools mean someone else's campaign can affect your password resets; separated streams (Postmark's Message Streams, Lettr's transactional and marketing streams) contain the damage.
• Analytics granularity and retention. Per-email event history versus aggregate counters, and for how long. Retention is a hidden pricing lever: Mailgun keeps logs 1 to 30 days depending on plan, MailerSend 24 hours on its free tier, Postmark 45 days by default.
• Template tooling. Bring-your-own-HTML (SES), templates-in-code (Resend), or a visual builder (Lettr, MailerSend, Brevo). This decides whether a copy change needs a deploy.
• Support and onboarding friction. The most common complaint across review sites is not features but accounts: suspensions without explanation and support gated behind top tiers, particularly at the acquired providers (SendGrid under Twilio, Mailgun under Sinch, Postmark under ActiveCampaign).

Pricing across the category is volume-based: the bill follows emails sent, not contacts stored. Anyone arriving from a Mailchimp-style marketing platform should expect that model change, and it usually works in the sender's favor for transactional traffic.

Pricing at a glance

Monthly prices for two common volumes, plus each service's free tier, as published in July 2026. Free tiers have been shrinking across the industry (SendGrid removed its entirely, MailerSend cut its from 3,000 to 500 emails), so treat this column as the most volatile.

The nine services

Lettr

Lettr sends over both a REST API and an SMTP relay, and its distinguishing feature is per-email statistics: opens, clicks, bounces, and delivery state are stored and searchable for every individual message, not aggregated into daily counters. Templates are built in the Topol drag-and-drop editor with a full template language (conditionals, loops, snippets), tracking domains run over HTTPS, and deliverability alerts report sudden bounce-rate jumps and blocklist appearances as they happen.

Marketing email is included rather than a separate product: Audiences and Campaigns run in the same account on separate sending streams, so campaign complaints never touch transactional reputation. The free tier is 3,000 emails a month with no expiry, and paid pricing ($15 for 50,000, $30 for 100,000) sits at roughly half of Mailgun and a quarter of Postmark. The pricing page has the full ladder. The honest tradeoff: Lettr is younger than the incumbents, which is also why it is priced under them.

Postmark

Postmark has spent a decade optimizing for transactional deliverability and speed, and independent tests keep confirming it: Mailtrap's 2026 comparison measured it highest of the services tested at 83.3% inbox placement. Message Streams keep transactional and broadcast traffic on separate IP pools by design. The price reflects the reputation: roughly $133.50 a month at 100,000 emails on the Pro plan, and a dedicated IP requires 300,000 emails a month plus $50. Since the ActiveCampaign acquisition, reviews increasingly mention stricter account approval and slower support, a shift from its Wildbit-era reputation. See how it stacks up against Lettr feature by feature on the Postmark comparison.

Twilio SendGrid

SendGrid is the biggest name in the category and the safest choice on paper for enterprise scale, with volume pricing that stays reasonable ($34.95 at 100,000 on Essentials). Two caveats have grown in recent years. First, the free plan is gone: retired in May 2025, replaced by a 60-day trial capped at 100 emails a day. Second, support and account management draw persistent complaints (a 1.2/5 Trustpilot average, with account suspensions a recurring theme), and meaningful support is effectively gated behind the $89.95 Pro tier, which is also where dedicated IPs start. Shared-IP senders inherited a rough patch in early 2025 when Microsoft temporarily blocked SendGrid shared-pool traffic. The SendGrid comparison covers the feature differences.

Mailgun

Mailgun remains a developer favorite for its API, routing, and validation tooling, and it is one of the clearest choices for EU data residency, with a dedicated EU region where message data never leaves the region. Pricing has crept upward since the Sinch acquisition ($35 at 50,000, $90 at 100,000 on Scale), log retention is short on lower tiers (1 to 5 days), and review sites echo the same acquisition-era support complaints as SendGrid. Feature comparison: Mailgun vs. Lettr.

Amazon SES

SES is the cheapest option by a wide margin: $0.10 per 1,000 emails, about $10 a month at 100,000. The price covers sending only, because SES is raw infrastructure. There is no template builder, minimal dashboarding, and bounce handling, suppression, and analytics have to be assembled from SNS topics and CloudWatch. New accounts start in a sandbox capped at 200 emails a day until production access is approved, and AWS enforces bounce and complaint thresholds automatically. SES is the right answer for teams with the engineering time to build around it; the hidden cost of DIY transactional email is the counterargument, and this page compares the alternatives.

Resend

Resend is the default in the modern JavaScript ecosystem, and deservedly so for developer experience: a clean API, official SDKs in nine languages, React Email for templates-in-code, and a 3,000-email monthly free tier. It also picked up much of SendGrid's departing free-tier audience in 2025. The limits show up after launch: analytics are thin compared to Mailgun or Postmark, data retention is 30 days outside Enterprise, and dedicated IPs require the $90 Scale plan. Pricing is otherwise competitive at $20 for 50,000 and $35 for 100,000. The Resend comparison details where the two products differ.

MailerSend

MailerSend pairs a developer API with a drag-and-drop template builder inherited from MailerLite, a combination rare at its price point ($35 at 50,000). Its recent direction is worth knowing: the free tier shrank from 3,000 emails to 500 in late 2025 (with a credit card now required), activity retention is 24 hours on the free plan and 7 days on Starter, and account approval is strict enough that rejected signups are a recurring review theme. MailerSend vs. Lettr has the feature breakdown.

Brevo

Brevo (formerly Sendinblue) bundles marketing and transactional email into one inexpensive platform, with a perpetual 300-email-a-day free tier and 100,000 transactional emails for $69 on Starter. The architecture is the tradeoff: transactional mail shares infrastructure with marketing traffic, and measured placement reflects it (roughly 87% overall in one 2026 test, with Gmail placement as low as 72%, and slower delivery than the transactional specialists). A reasonable pick when one cheap tool for everything matters more than transactional performance.

SMTP2GO

SMTP2GO posted the best deliverability numbers in the field: EmailTooltester's 2026 four-round test measured 95.5% average inbox placement, and reviews consistently praise its human support. The product is relay-first and simpler than the API-first providers (no SSO, no HIPAA option, reporting retention 30 days on paid plans), and pricing lands mid-pack: $10 for 10,000 on Starter, $75 for 100,000 on Professional with a dedicated IP included. A strong fit for teams that mainly need a reliable SMTP relay with people answering the support inbox.

Which one to pick

• Lowest cost at scale, engineering time available: Amazon SES, with the understanding that the tooling around it is yours to build and operate.
• Maximum deliverability pedigree, price secondary: Postmark, or SMTP2GO for a relay-first setup with the best measured placement.
• Modern developer experience on a JS stack: Resend, if aggregate analytics and 30-day retention are enough.
• Per-email analytics, visual templates, and marketing in one account: Lettr, at $30 for 100,000 emails with both API and SMTP transports.
• EU data residency as a hard requirement: Mailgun's EU region, or Brevo as an EU-headquartered all-in-one.
• Enterprise procurement and the Twilio ecosystem: SendGrid, budgeting for the Pro tier where support and dedicated IPs live.

FAQ

Bottom line

The category splits into three tiers: raw infrastructure (SES) for teams that want to build, premium specialists (Postmark) for teams that want a track record at any price, and a broad middle where price, analytics, and tooling decide. Free tiers are the fastest way to compare the middle tier, since setup on any of these services takes minutes rather than days.

Lettr's free tier is 3,000 emails a month with per-email analytics, both transports, and the template builder included. Create a free account and send a real message through the API or the relay before committing to anything.