established · 0.1

Transactional Email

Score 25.9 / 100 38 providers +4 via APIs 12 APIs Search apis.io →
Variants seen in the corpus: Transactional EmailTransactional email

Providers using this tag (38)

Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.

Exemplar 17 Complete, well-documented, and agent-ready
Customer.ioBehavioral DataBroadcastsCampaignsCDP4 APIs89.3BrevoMarketingMarketing AutomationEmail Marketing21 APIs87.3AhaSendEmailDeveloper ToolsSMTP2 APIs82.3SendGridEmailEmail APIMarketing EmailSMTP44 APIs80.0MailchimpCampaignsEmail MarketingMarketing AutomationNewsletters4 APIs77.8MailerLiteEmail MarketingAutomationNewslettersSubscribers1 API77.3Amazon SESEmailEmail DeliverabilityEmail ServiceMarketing Email2 APIs76.3PlunkEmailMarketingAutomation2 APIs74.6SendPulseMarketingMarketing AutomationEmail20 APIs74.4GetResponseEmail MarketingMarketing AutomationLanding PagesWebinars50 APIs74.3SMTP2GOEmailEmail DeliverySMTP1 API71.7PauboxEmailHIPAAHealthcareCompliance3 APIs71.5PostmarkEmailsMessagingDeliverability3 APIs71.3OrttoMarketing AutomationCDPCustomer Data PlatformAnalytics1 API70.5Campaign MonitorEmail MarketingCampaignsSubscribers1 API70.0LoopsEmailEmail APIMarketing Automation1 API69.1Zoho CampaignsEmail MarketingCampaignsMailing ListsSubscribers2 APIs68.9
Strong 8 Solid coverage with minor gaps
MoosendEmail MarketingMarketing AutomationCampaignsMailing Lists1 API65.8MailmodoEmailInteractive EmailAMP for EmailMarketing Automation9 APIs63.7SilverpopEmail MarketingMarketing AutomationCampaign ManagementDigital Marketing1 API63.3EnchargeEmail MarketingMarketing AutomationSoftware-as-a-Service1 API63.2Benchmark EmailEmail MarketingCampaignsContactsAutomation2 APIs62.9DotdigitalMarketing AutomationEmail MarketingSMSMMS86 APIs62.8EmailOctopusEmailEmail MarketingNewslettersCampaigns2 APIs61.1MailerSendEmailSMTPMarketing1 API60.6
Developing 8 Usable, with meaningful gaps to close
SailthruCompanyEmail MarketingMarketing AutomationPersonalization2 APIs54.2ResendEmailDeveloper ToolsMarketing Email1 API53.5listmonkEmailNewsletterMailing ListMarketing2 APIs48.0CommsHarborEmailEmail MarketingCommunications1 API45.6LoopsEmailMarketing EmailEmail Automation1 API45.4SparkPostEmailMarketing EmailEmail Delivery10 APIs45.4MailjetEmailEmail DeliveryMarketing EmailSMTP1 API43.4MailtrapEmailEmail DeliveryEmail SandboxEmail Testing2 APIs39.7
Thin 4 Limited public surface area
MailerooEmailEmail DeliveryMarketing EmailSMTP1 API38.9MailPaceEmailMessagingSMTP1 API35.8SendHQEmail APIInbound EmailDeliverability2 APIs33.5MailgunEmailSMTPEmail Validation1 API33.0
Emerging 1 Early or largely undocumented
InboxEmailInboxMessagingDeliverability2 APIs21.4

APIs with this tag (11)

Ranked by the provider's API Evangelist rating — the Kin Score is scored per provider, not per API, so every API of a provider shares its band. How the rating works →

Exemplar 3 Complete, well-documented, and agent-ready
HubSpot Transactional Email APIThe transactional email API enables sending template-based transactional emails through HubSpot using the S...87.1Campaign Monitor APIREST API for managing email campaigns, subscriber lists, transactional emails, segments, journeys, template...70.0Zoho Campaigns Email APIResource-oriented JSON REST API for sending email at volume from Zoho Campaigns. Covers transmissions (crea...68.9
Strong 2 Solid coverage with minor gaps
Encharge Transactional Email APIREST API for sending transactional emails through Encharge. Accepts JSON at POST /v1/emails/send with exact...63.2Dotdigital Transactional email APIThe Transactional email API from Dotdigital — 5 operation(s) for transactional email.62.8
Developing 4 Usable, with meaningful gaps to close
Sailthru APIThe core Sailthru HTTPS API. All requests are GET, POST or DELETE calls to https://api.sailthru.com/, auth54.2Zoho ZeptoMailThe Zoho ZeptoMail API provides REST endpoints for sending transactional emails such as OTPs, password rese...54.1Kaleyra Email APISend single and batch transactional email (Email API v2) with domain management, templates, webhooks, and d...53.7CommsHarbor APIREST/HTTP API (OpenAPI 3.1) for transactional email, deliverability, sending domains, permission-based mark...45.6
Thin 1 Limited public surface area
SendHQ REST APIResend-compatible REST API for transactional and inbound email, domains, templates, deliverability, and wor...33.5
Emerging 1 Early or largely undocumented
Mailgun Email APIMailgun provides a programmable email API for sending, receiving, tracking, and validating email at scale. ...21.4

Companies reaching this through an API (4)

These companies publish an API, specification or operation carrying “Transactional Email” but do not classify their business under it. Listed unranked and kept out of the count above, because one tagged operation is not a statement about what a company does.

HubSpot Kaleyra Proofpoint Zoho

Score breakdown

Frequency
46.9
log-scaled weighted occurrences
Breadth
1.0
spread across providers
Quality lift
69.5
mean composite of providers using it
Cohesion
0.0
strength of nearest seed neighbor

Related tags

SMTP 14 co-occurrences Email Delivery 8 co-occurrences Marketing Email 7 co-occurrences Email Marketing 18 co-occurrences Deliverability 10 co-occurrences Transactional 7 co-occurrences Email API 6 co-occurrences Mailing Lists 6 co-occurrences

Where this tag comes from

Provider tag38
Api tag12
Openapi tag1
Openapi op tag5

Cohort brief

Auto-generated

The 38 providers in the APIs.io catalog tagged Transactional Email, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers
38
all scored
Mean Kin Score
61.3
+37.4 vs catalog 23.9
Mean Agent Readiness
37.2
+25.2 vs catalog 12
Spread
21.4–89.3
median 63.5 · σ 16.5
How the 38 split by band
Exemplar 17Strong 8Developing 8Thin 4Emerging 1Minimal 0
Facet averages, against the whole catalog
FacetThis cohortCatalogDifferenceScored
Access Clarity 73 26.5 +46.5 38
Operational Transparency 55.4 14 +41.4 38
Contract Quality 60 19.8 +40.2 38
Developer Ergonomics 62 23.4 +38.6 38
Discoverability 73.2 61.2 +12 38
Contract Governance 15.8 6.4 +9.4 38

A facet is averaged over the members that carry it, not over the whole cohort — the “Scored” column is that count. Averaging an absent facet as zero would score our own coverage gaps as the providers’ posture.

What this cohort publishes
ArtifactThis cohortCatalogDifference
MCP server (any) 47% 10% +37
MCP server (first-party) 53% 13% +40
Agent Skills 0% 0% 0
OAuth scopes 32% 11% +21
Security 97% 97% 0
Arazzo workflows 5% 2% +3
Governance rules 37% 14% +23

mcp_pct counts any mcp/ artifact including ones API Evangelist derived from the provider OpenAPI; mcp_first_party_pct counts only servers the provider publishes. Prefer the latter.

Top by Kin Score
  1. 1 Customer.io 89.3
  2. 2 Brevo 87.3
  3. 3 AhaSend 82.3
  4. 4 SendGrid 80
  5. 5 Mailchimp 77.8
  6. 6 MailerLite 77.3
  7. 7 Amazon SES 76.3
  8. 8 Plunk 74.6
  9. 9 SendPulse 74.4
  10. 10 GetResponse 74.3
Top by Agent Readiness
  1. 1 Loops 62.9
  2. 2 Customer.io 62.1
  3. 3 Paubox 61.5
  4. 4 MailerSend 55.4
  5. 5 Brevo 54.8
  6. 6 MailerLite 54.3
  7. 7 SendPulse 53.6
  8. 8 GetResponse 47.8
  9. 9 AhaSend 46.5
  10. 10 Mailmodo 42.8
All 38 members of this roster resolve to a scored provider in the catalog.Generated from the catalog build of 15 September 2026, across 27661 providers, using the same computation served by the APIs.io cohort API. Briefs are published for rosters of 5 or more scored providers; below that a distribution is not meaningful.

Work with this as data

Every tag here is available over the APIs.io API and to AI agents over MCP.

MCP server

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https://apis.io/mcp

Tools for tags

7 MCP tools reach this
  • find_tagsBrowse and filter every tag in the catalog.
  • get_cohortThis tag as a scored cohort — every provider carrying it, with scores.
  • cohort_statsPRO — the distribution across this tag: mean, median, band split, adoption rates.
  • cohort_rankingsPRO — the leaderboard, on composite AND agent-readiness axes.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

curl for this page
This tag 
curl "https://apis.io/api/v1/tags/transactional-email"
All tags 
curl "https://apis.io/api/v1/tags?limit=25"
As a scored cohort 
curl "https://apis.io/api/v1/cohorts/tag/transactional-email"
The distribution (Pro) 
curl "https://apis.io/api/v1/cohorts/tag/transactional-email/stats" \
  -H "X-API-Key: $APIS_IO_KEY"

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