Category · 7 services

Email API Services for Developers (2026)

Email API services give developers REST APIs, SDKs, webhooks and SMTP credentials to send and track email from their own code, with logs and event data for every message. 7 services are listed, each linked to its profile and, where they exist, its pricing and API pages.

Services listed: 7
Deliverability-tested: 7
With user ratings: 7
Marketing + transactional: 1

Computed from our datasets · InboxRatio Editorial

This page compares 7 email API services from the InboxRatio catalog, listed with measured deliverability first and catalog demand order after that. All 7 have a measured deliverability score from our own seed-list inbox placement tests, and the table shows each score with its band. By price level, 1 is budget ($), 4 SMB ($$) and 2 mid-market ($$$). 1 also runs bulk marketing campaigns from the same platform, flagged “Marketing + transactional” in the table. All 7 have user ratings collected from Trustpilot, G2 and Capterra, with Trustpilot counting for half; ratings are context and never feed the deliverability score. Counts, scores and order are computed from the same datasets as each service profile, so this page updates as new test cycles and data checks land. Plan-by-plan prices sit on the linked pricing pages.

Measured deliverability first · then catalog order

Email API Services for Developers compared

Service	Price level	Deliverability	User rating	Also covers	Details
Postmark	$$$ Mid-market	93/100Excellent	3.3	—	Pricing · API
Resend	$$ SMB	84/100Good	2.9	—	Pricing · API
MailerSend	$$ SMB	84/100Good	4.3	—	Pricing · API
SendGrid	$$ SMB	77/100Good	2.6	Marketing + transactional	Pricing · API
Mailtrap	$$ SMB	77/100Good	4.5	—	Pricing · API
Amazon SES	$ Budget	75/100Good	4.5	—	Pricing · API
Mailgun	$$$ Mid-market	72/100Fair	4.2	—	Pricing · API

Deliverability = our measured score from seed-list inbox placement tests (“Not yet tested” until a cycle publishes). User rating = combined Trustpilot, G2 and Capterra rating with Trustpilot counting for half — context only, never part of the score. “Marketing + transactional” = also sends the other kind of email from one platform.

Service cards

All 7 email API services

Postmark$$$
Transactional email service owned by ActiveCampaign, with API and SMTP sending for application email.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability93/100Excellent
User rating3.3
Global
Resend$$
Developer-first transactional email API; a separately priced marketing product exists alongside.
Official MCPTransactional Email Developer Email Infrastructure
Deliverability84/100Good
User rating2.9
Global
MailerSend$$
Transactional email API and SMTP service from the makers of MailerLite, with per-volume pricing in USD.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability84/100Good
User rating4.3
Global
SendGrid$$
Transactional email API and SMTP service operated by Twilio, with a separate Marketing Campaigns product; the transactional demand anchor.
Marketing + transactional Transactional Email SMTP Provider Developer Email Infrastructure Email Marketing
Deliverability77/100Good
User rating2.6
Global
Mailtrap$$
Email delivery platform combining a sending API/SMTP service with a testing sandbox; each product is priced separately.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability77/100Good
User rating4.5
Global
Amazon SES$
AWS's usage-priced transactional email service — the price floor of our transactional category at 50,000 emails/month.
Transactional Email SMTP Provider Developer Email Infrastructure
Deliverability75/100Good
User rating4.5
Global
Mailgun$$$
Transactional email API and SMTP relay for developer sending, owned by Sinch.
Official MCPTransactional Email SMTP Provider Developer Email Infrastructure
Deliverability72/100Fair
User rating4.2
Global

Generated from our datasets — every value verified and dated

Frequently asked questions

How many email API services have been deliverability-tested?

All 7 have a published score from our own seed-list inbox placement tests. Highest measured so far: Postmark (93/100), Resend (84/100) and MailerSend (84/100). Full deliverability ranking.

Which email API services have the highest user ratings?

Among those with at least 100 reviews: Mailtrap (4.5/5 across 132 reviews), Amazon SES (4.5/5 across 326 reviews) and MailerSend (4.3/5 across 331 reviews), on the combined Trustpilot, G2 and Capterra rating in which Trustpilot counts for half. User ratings are context from review platforms, not part of our measured deliverability score. All services by user rating.

Which email API services also handle email marketing campaigns?

SendGrid: 1 of the 7 sends bulk campaigns and transactional or SMTP email from one platform.

How much do email API services cost?

Price levels run from budget ($) to enterprise ($$$$). Of the 7 listed here, 1 is budget ($), 4 SMB ($$) and 2 mid-market ($$$). Plan prices by volume, from each vendor's official pricing page, are on the pricing hub. Transactional Email pricing.

How are the email API services on this page ordered?

Services with a published deliverability score come first, highest score first; the rest follow the catalog's demand order, which sorts services by search demand within each review tier. The order is computed by the same rule for every vendor and never hand-picked. Our methodology.