emerging · -1.7 market domain

SMTP

Score 21.4 / 100 25 providers +7 via APIs 8 APIs Search apis.io →
Variants seen in the corpus: Simple Mail Transfer ProtocolSMTP

Providers using this tag (25)

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

Exemplar 7 Complete, well-documented, and agent-ready
AhaSendEmailTransactional EmailDeveloper Tools2 APIs90.5SendGridEmailEmail APIMarketing Email44 APIs84.0SMTP2GOEmailEmail DeliveryTransactional Email1 API71.1PostmarkEmailMessagingTransactional EmailDeliverability3 APIs70.5MailboxlayerEmailEmail VerificationMX Records2 APIs67.8Amazon SESAmazon Web ServicesEmailEmail DeliverabilityEmail Service31 APIs83.8MailosaurEmail TestingSMS TestingDeveloper ToolsQA Automation1 API68.0
Strong 4 Solid coverage with minor gaps
groundmail-devEmailTransactionalDevelopers1 API61.3MailerSendEmailTransactional EmailMarketing1 API57.5AgentMailCompanyArtificial IntelligenceEmailAI Agents1 API62.2MoosendEmail MarketingMarketing AutomationCampaignsMailing Lists1 API60.3
Developing 7 Usable, with meaningful gaps to close
checkmailsCompanyEmail VerificationGDPR1 API49.9uCheckerEmail VerificationEmailDNS1 API49.4securessmtp-comEmailTransactionalServices2 APIs46.5MailChannelsCompanyEmailPlatform44.7adbtdEmail InfrastructureIMAPDedicated IP1 API43.9MailBridgeAPIEmail APIIMAPmailbox integration1 API43.7MailjetEmailEmail DeliveryMarketing Email1 API50.5
Thin 6 Limited public surface area
Apache JamesEmailIMAPJavaJMAP1 API39.1MailerooEmailEmail DeliveryMarketing Email1 API36.1MailgunEmailTransactional EmailEmail Verification1 API31.6EmailEngineEmailEmail APIIMAP13 APIs27.6MailPaceEmailTransactional EmailMessaging1 API26.6SparkPostEmailTransactional EmailMarketing EmailEmail Delivery10 APIs37.1
Minimal 1 Almost no public developer surface
PostfixEmailMail ServerMTA1 API9.0

APIs with this tag (8)

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 2 Complete, well-documented, and agent-ready
HubSpot Transactional Email APIThe transactional email API enables sending template-based transactional emails through HubSpot using the S...91.9Harness SMTP APIThis contains APIs related to SmtpConfig as defined in Harness87.7
Strong 3 Solid coverage with minor gaps
Zoho ZeptoMailThe Zoho ZeptoMail API provides REST endpoints for sending transactional emails such as OTPs, password rese...63.7Smartlead Email Accounts APIEndpoints to add, list, update, and remove sender mailboxes (SMTP, Gmail, Outlook), assign them to campaign...60.2Cisco Intersight Smtp APIThe smtp API from Cisco Intersight — 6 operation(s) for smtp.60.1
Developing 2 Usable, with meaningful gaps to close
Pure Storage SMTP APIManages Simple Mail Transfer Protocol (SMTP) settings. SMTP allows the array to send email notifications an...47.7MagicBell Smtp APIThe smtp API from MagicBell — 1 operation(s) for smtp.45.8
Minimal 1 Almost no public developer surface
Postfix SMTPPostfix implements SMTP (RFC 5321) for sending and receiving electronic mail, with submission (port 587), S...9.0

Companies reaching this through an API (7)

These companies publish an API, specification or operation carrying “SMTP” 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.

Cisco Intersight Harness HubSpot MagicBell Pure Storage Smartlead Zoho

Score breakdown

Frequency
39.6
log-scaled weighted occurrences
Breadth
0.3
spread across providers
Quality lift
52.5
mean composite of providers using it
Cohesion
5.8
strength of nearest seed neighbor

Where this tag sits

Email broader

Related tags

Transactional Email 14 co-occurrences Deliverability 11 co-occurrences Email Delivery 6 co-occurrences Marketing Email 5 co-occurrences IMAP 5 co-occurrences Email API 5 co-occurrences Email 24 co-occurrences

Where this tag comes from

Provider tag25
Api tag8
Openapi tag2
Openapi op tag7

Markets provisional

Kin Score markets whose measured providers carry this tag. Share is the fraction of the market's measured providers that carry it — it describes the market, not this tag.

MarketShare of the market's providers
Communications (CPaaS)24%

Cohort brief

Auto-generated

The 25 providers in the APIs.io catalog tagged SMTP, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers
25
all scored
Mean Kin Score
52.5
+28.4 vs catalog 24.1
Mean Agent Readiness
33.4
+19.3 vs catalog 14.1
Spread
9–90.5
median 49.9 · σ 19.4
How the 25 split by band
Exemplar 7Strong 4Developing 7Thin 6Emerging 0Minimal 1
Facet averages, against the whole catalog
FacetThis cohortCatalogDifferenceScored
Contract Quality 50.6 18.6 +32 25
Developer Ergonomics 56.2 24.5 +31.7 25
Access Clarity 59.8 30 +29.8 25
Operational Transparency 41 13.2 +27.8 25
Contract Governance 23.5 9.7 +13.8 25
Discoverability 70.5 59.1 +11.4 25

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) 32% 18% +14
MCP server (first-party) 36% 16% +20
Agent Skills 0% 0% 0
OAuth scopes 12% 13% -1
Security 100% 99% +1
Arazzo workflows 4% 1% +3
Governance rules 96% 36% +60

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 AhaSend 90.5
  2. 2 SendGrid 84
  3. 3 Amazon SES 83.8
  4. 4 SMTP2GO 71.1
  5. 5 Postmark 70.5
  6. 6 Mailosaur 68
  7. 7 Mailboxlayer 67.8
  8. 8 AgentMail 62.2
  9. 9 groundmail-dev 61.3
  10. 10 Moosend 60.3
Top by Agent Readiness
  1. 1 AgentMail 64.6
  2. 2 AhaSend 58.7
  3. 3 groundmail-dev 57.3
  4. 4 MailerSend 56.3
  5. 5 uChecker 44.3
  6. 6 Postmark 41.7
  7. 7 SendGrid 40.1
  8. 8 SMTP2GO 39.1
  9. 9 securessmtp-com 39.1
  10. 10 Amazon SES 38.4
All 25 members of this roster resolve to a scored provider in the catalog.Generated from the catalog build of 14 November 2026, across 41591 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

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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 →

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