Applications › Email Client & Hosting

Email Client & Hosting

What 7 leading Email Client & Hosting apps are built on: the providers each one ships in its code or lists as an integration, grouped by layer and capability, and joined to the catalog.

7 reference apps 58 providers 58 observed in code 0 declared only 98.3% in the catalog 40.8 mean Kin Score 22 with a verified MCP server
How to read this. observed the integration ships in the app (SDK in a dependency file, source code, or an Android build analysis). declared the app names the integration itself (README, integrations page, store listing). Every row links the source it was read from. Providers not yet in the catalog are marked queued for profiling. Blueprint by API Evangelist, CC BY-NC-SA 4.0. Capabilities marked Turbo EA come from Turbo EA Capabilities by Vincent Verdet, CC BY 4.0 (notice); those marked API Evangelist extension are CC BY-NC-SA 4.0.

domain layer 5 capabilities
Mailbox & Calendar Sync 14 providers · AE-150.80 · API Evangelist extension

Mailbox & Calendar Sync capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Outlook.com observed [1] [2] [3] FairEmail, Roundcube Webmail, Thunderbird for Android 65.9 strong 48.6 agent-ready verified
Gmail observed [1] [2] [3] FairEmail, Roundcube Webmail, Thunderbird for Android 44.1 developing 19.6 agent-aware verified
AOL Mail observed [1] [2] FairEmail, Thunderbird for Android 44.6 developing 36.1 agent-ready none found
Yahoo Mail observed [1] [2] FairEmail, Thunderbird for Android 41.4 developing 16.2 agent-aware none found
Fastmail observed [1] [2] FairEmail, Thunderbird for Android 38.1 thin 17.6 agent-aware none found
Microsoft Graph observed [1] FairEmail 61.0 strong 32.7 agent-ready verified
Apple iCloud Mail observed [1] FairEmail 55.2 strong 31.9 agent-ready none found
Zoho Mail observed [1] FairEmail 34.7 thin 24.6 agent-aware none found
Nextcloud observed [1] Mail-in-a-Box 31.3 thin 19.0 agent-aware none found
IONOS observed [1] FairEmail 29.5 thin 10.8 agent-aware verified
mailbox.org observed [1] FairEmail 23.4 emerging 30.6 agent-ready unknown
Yandex Mail observed [1] FairEmail 23.1 emerging 0.0 human-only —
GMX Mail observed [1] FairEmail 19.0 emerging 2.9 human-only none found
Posteo observed [1] FairEmail 16.5 emerging 0.0 human-only none found
Email Security 6 providers · AE-150.10.40 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
Spamhaus observed [1] [2] [3] FairEmail, Mail-in-a-Box, mailcow: dockerized 18.4 emerging 2.9 human-only —
VirusTotal observed [1] FairEmail 40.1 developing 30.9 agent-ready verified
NordSpam observed [1] FairEmail 12.0 emerging 2.5 human-only —
SpamCop observed [1] FairEmail 3.4 minimal 0.0 human-only —
UCEPROTECT observed [1] FairEmail 3.1 minimal 0.0 human-only —
Barracuda Networks observed [1] FairEmail 1.8 minimal 0.0 human-only none found
Search and Discovery Management 2 providers · BC-830.20.30 · Turbo EA
ProviderEvidenceAppsKin ScoreAgent readinessMCP
Elasticsearch observed [1] Stalwart Mail Server 76.1 exemplar 28.6 agent-ready verified
Meilisearch observed [1] Stalwart Mail Server 52.0 developing 24.4 agent-aware verified
Grammar & Writing Assistance 1 providers · AE-110.40.40 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
LanguageTool observed [1] FairEmail 28.3 thin 19.0 agent-aware none found
Machine Translation 1 providers · AE-110.40.10 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
DeepL observed [1] FairEmail 59.8 strong 36.4 agent-ready verified

common layer 11 capabilities
Domain Registration & Managed DNS 11 providers · AE-927 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
Cloudflare observed [1] Stalwart Mail Server 82.1 exemplar 69.6 agent-native verified
Linode observed [1] Stalwart Mail Server 57.8 strong 42.1 agent-ready verified
Google Cloud DNS observed [1] Stalwart Mail Server 57.2 strong 26.4 agent-aware none found
Amazon Route 53 observed [1] Stalwart Mail Server 55.4 strong 27.7 agent-aware none found
DigitalOcean observed [1] Stalwart Mail Server 45.0 developing 44.6 agent-ready verified
OVHcloud observed [1] Stalwart Mail Server 40.3 developing 28.1 agent-aware verified
bunny.net observed [1] Stalwart Mail Server 39.1 thin 26.1 agent-aware none found
Hetzner observed [1] Stalwart Mail Server 38.0 thin 26.3 agent-aware none found
Gandi observed [1] Stalwart Mail Server 27.3 thin 18.6 agent-aware none found
deSEC observed [1] Stalwart Mail Server 12.5 emerging 0.0 human-only —
Porkbun queued for profiling observed [1] Stalwart Mail Server — — —
Web Hosting & Control Panels 8 providers · AE-926 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
cPanel observed [1] Roundcube Webmail 66.3 strong 54.9 agent-ready none found
Plesk observed [1] Roundcube Webmail 44.3 developing 19.7 agent-aware —
Modoboa observed [1] Roundcube Webmail 40.0 developing 26.5 agent-aware —
Mail-in-a-Box observed [1] Roundcube Webmail 33.1 thin 22.6 agent-aware —
Stalwart observed [1] Roundcube Webmail 32.6 thin 15.1 agent-aware —
DirectAdmin observed [1] Roundcube Webmail 27.8 thin 17.6 agent-aware —
DomainFactory observed [1] Roundcube Webmail 12.8 emerging 2.9 human-only —
mailcow observed [1] Roundcube Webmail 12.6 emerging 14.4 agent-aware none found
Asset Storage & Tiering 3 providers · BC-3710.30 · Turbo EA

Asset Storage & Tiering capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Amazon S3 observed [1] [2] Mail-in-a-Box, Stalwart Mail Server 70.8 exemplar 23.3 agent-aware verified
Azure Blob Storage observed [1] Stalwart Mail Server 55.5 strong 26.9 agent-aware verified
Backblaze B2 observed [1] Mail-in-a-Box 50.9 developing 31.9 agent-ready verified
Credential Security 1 providers · AE-160.60 · API Evangelist extension

Credential Security capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Have I Been Pwned observed [1] [2] FairEmail, Roundcube Webmail 47.3 developing 31.0 agent-ready none found
Cryptography and Key Management 1 providers · BC-620.50.50 · Turbo EA
ProviderEvidenceAppsKin ScoreAgent readinessMCP
Let's Encrypt observed [1] [2] Mail-in-a-Box, mailcow: dockerized 22.7 emerging 17.2 agent-aware none found
IP Geolocation 2 providers · AE-120.50.10 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
IPinfo observed [1] FairEmail 62.5 strong 34.4 agent-ready verified
IP2Location observed [1] FairEmail 5.2 minimal 0.0 human-only verified
In-App Purchases & App Store Billing 1 providers · AE-904 · API Evangelist extension

In-App Purchases & App Store Billing capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Google Play Billing observed [1] [2] Proton Mail (Android), Thunderbird for Android 31.6 thin 24.6 agent-aware none found
Managed Operational Databases 1 providers · AE-915 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
Redis observed [1] Stalwart Mail Server 47.4 developing 49.8 agent-native verified
Observability Management 1 providers · BC-4220.20 · Turbo EA

Observability Management capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Sentry observed [1] Proton Mail (Android) 80.6 exemplar 50.2 agent-ready verified
Product Usage Analytics 1 providers · BC-4280.30 · Turbo EA

Product Usage Analytics capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Mozilla Glean observed [1] Thunderbird for Android 24.1 emerging 24.1 agent-aware —
Push Notifications 1 providers · AE-150.30 · API Evangelist extension

Push Notifications capability

ProviderEvidenceAppsKin ScoreAgent readinessMCP
Firebase Cloud Messaging observed [1] Proton Mail (Android) 50.3 developing 14.2 agent-aware verified

agent layer 1 capabilities
Hosted LLM Inference 3 providers · AE-110.10.10 · API Evangelist extension
ProviderEvidenceAppsKin ScoreAgent readinessMCP
OpenAI observed [1] [2] FairEmail, Stalwart Mail Server 83.0 exemplar 58.4 agent-native verified
Google Gemini observed [1] [2] FairEmail, Stalwart Mail Server 55.1 strong 31.3 agent-ready none found
Anthropic observed [1] Stalwart Mail Server 89.0 exemplar 47.6 agent-ready verified

Reference apps

FairEmail open-source-saas

https://github.com/M66B/FairEmail

26 observed · 0 declared
  • observed ships the AOL Mail SDK or integration code source
  • observed ships the Apple iCloud Mail SDK or integration code source
  • observed ships the Barracuda Networks SDK or integration code source
  • observed ships the DeepL SDK or integration code source
  • observed ships the Fastmail SDK or integration code source
  • observed ships the Gmail SDK or integration code source
  • observed ships the GMX Mail SDK or integration code source
  • observed ships the Google Gemini SDK or integration code source
  • observed ships the Have I Been Pwned SDK or integration code source
  • observed ships the IONOS SDK or integration code source
  • observed ships the IP2Location SDK or integration code source
  • observed ships the IPinfo SDK or integration code source
  • observed ships the LanguageTool SDK or integration code source
  • observed ships the mailbox.org SDK or integration code source
  • observed ships the Microsoft Graph SDK or integration code source
  • observed ships the NordSpam SDK or integration code source
  • observed ships the OpenAI SDK or integration code source
  • observed ships the Outlook.com SDK or integration code source
  • observed ships the Posteo SDK or integration code source
  • observed ships the SpamCop SDK or integration code source
  • observed ships the Spamhaus SDK or integration code source
  • observed ships the UCEPROTECT SDK or integration code source
  • observed ships the VirusTotal SDK or integration code source
  • observed ships the Yahoo Mail SDK or integration code source
  • observed ships the Yandex Mail SDK or integration code source
  • observed ships the Zoho Mail SDK or integration code source

Read from: source code, source code, source code

Thunderbird for Android open-source-saas

https://github.com/thunderbird/thunderbird-android

7 observed · 0 declared
  • observed ships the AOL Mail SDK or integration code source
  • observed ships the Fastmail SDK or integration code source
  • observed ships the Gmail SDK or integration code source
  • observed ships the Google Play Billing SDK or integration code source
  • observed ships the Mozilla Glean SDK or integration code source
  • observed ships the Outlook / Microsoft 365 SDK or integration code source
  • observed ships the Yahoo Mail SDK or integration code source

Read from: dependency manifest, source code

Proton Mail (Android) open-source-saas

https://github.com/ProtonMail/android-mail

3 observed · 0 declared
  • observed ships the Firebase Cloud Messaging SDK or integration code source
  • observed ships the Google Play Billing SDK or integration code source
  • observed ships the Sentry SDK or integration code source

Read from: dependency manifest

mailcow: dockerized self-hosted

https://github.com/mailcow/mailcow-dockerized

2 observed · 0 declared
  • observed ships the Let's Encrypt SDK or integration code source
  • observed ships the Spamhaus SDK or integration code source

Read from: source code, source code

Mail-in-a-Box self-hosted

https://github.com/mail-in-a-box/mailinabox

5 observed · 0 declared
  • observed ships the Amazon S3 SDK or integration code source
  • observed ships the Backblaze B2 SDK or integration code source
  • observed ships the Let's Encrypt SDK or integration code source
  • observed ships the Nextcloud SDK or integration code source
  • observed ships the Spamhaus SDK or integration code source

Read from: source code, source code, source code

Stalwart Mail Server self-hosted

https://github.com/stalwartlabs/stalwart

19 observed · 0 declared
  • observed ships the Amazon Route 53 SDK or integration code source
  • observed ships the Amazon S3 SDK or integration code source
  • observed ships the Anthropic SDK or integration code source
  • observed ships the Azure Blob Storage SDK or integration code source
  • observed ships the bunny.net SDK or integration code source
  • observed ships the Cloudflare SDK or integration code source
  • observed ships the deSEC SDK or integration code source
  • observed ships the DigitalOcean SDK or integration code source
  • observed ships the Elasticsearch SDK or integration code source
  • observed ships the Gandi SDK or integration code source
  • observed ships the Google Cloud DNS SDK or integration code source
  • observed ships the Google Gemini SDK or integration code source
  • observed ships the Hetzner SDK or integration code source
  • observed ships the Linode SDK or integration code source
  • observed ships the Meilisearch SDK or integration code source
  • observed ships the OpenAI SDK or integration code source
  • observed ships the OVHcloud SDK or integration code source
  • observed ships the Porkbun SDK or integration code source
  • observed ships the Redis SDK or integration code source

Read from: dependency manifest, source code, source code

Roundcube Webmail self-hosted

https://github.com/roundcube/roundcubemail

9 observed · 2 declared
  • observed ships the cPanel SDK or integration code source
  • observed ships the DirectAdmin SDK or integration code source
  • observed ships the DomainFactory SDK or integration code source
  • observed ships the Have I Been Pwned SDK or integration code source
  • observed ships the Mail-in-a-Box SDK or integration code source
  • observed ships the mailcow SDK or integration code source
  • observed ships the Modoboa SDK or integration code source
  • observed ships the Plesk SDK or integration code source
  • observed ships the Stalwart SDK or integration code source
  • declared lists Gmail as an integration source
  • declared lists Outlook.com as an integration source

Read from: source code, source code

Where these apps are listed

See also the shared layer under every category.