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Technologies / Anthropic / Fastmail

Companies using Anthropic and Fastmail

6 companies in our data have public evidence for both Anthropic and Fastmail, and 6 name both in their own subprocessor list. Each company below links to the source for every claim. Our coverage is partial, so this is not everyone.

6companies use both
under 1%of Anthropic users
40%of Fastmail users
6name both as subprocessors

Companies using one are 3.2 times as likely as the average company in our data to show evidence of the other.

The companies

Strongest evidence first: a company naming both in its own subprocessor list comes before one seen on its website or in job postings.

Subprocessor listPrivacy policyWebsiteJob postings

CompanyAnthropicFastmail
Auth57 Labsauth57.ioAuth57 provides verified prior-authorization rule data for drugs, procedures, and services across all 51 states.Healthcare
Auth57 Labsauth57labs.comAuth57 provides verified prior authorization rule data for drugs, procedures, and services across all 51 states.Healthcare
draw.io
Sendmarcsendmarc.comSendmarc provides a platform for managing DMARC, SPF, and DKIM email authentication across domains.Cybersecurity
SimpleLocalizesimplelocalize.ioSimpleLocalize provides a web-based translation editor and platform for managing translations and automating localization workflows for software projects.Developer tools
Fathom Analyticsusefathom.comFathom provides website analytics software that shows where visitors come from, which pages they read, and what converts without using cookies.Data and analytics

The two technologies

Anthropic

AI and LLM providers

Anthropic is a public benefit corporation dedicated to securing the benefits of AI and mitigating its risks. It is used for the responsible development and maintenance of advanced AI for the long-term benefit of humanity.

Summarized from anthropic.com on 8 Nov 2026.

under 1% of the 2,926 companies we see using Anthropic also show the other.

All 2,926 companies using Anthropic2,246 name it as a subprocessorMore in AI and LLM providers

Fastmail

Email and communications

Fastmail is a paid email hosting service offering email, calendar, and contacts, with options for private email addresses and offline access. It is used by individuals and businesses to send, receive, organize, and manage email, calendars, and contacts across devices.

Summarized from fastmail.com on 8 Nov 2026.

40% of the 15 companies we see using Fastmail also show the other.

All 15 companies using Fastmail12 name it as a subprocessorMore in Email and communications

Other pairs

Companies with their own evidence for both.

More with Anthropic

Cloudflare2,905companiesGoogle Workspace2,134companiesOpenAI1,997companiesAmazon Web Services1,554companiesStripe1,534companiesGoogle1,415companies

More with Fastmail

Cloudflare16companiesStripe10companiesAmazon Web Services6companiesHetzner6companiesGoogle5companiesPaddle5companies

Questions

How many companies use both Anthropic and Fastmail?

6 companies in StrataDB's data have public evidence for both, and 6 of them name both in their own subprocessor list, the strongest evidence we hold. Our coverage is partial, so the real number is higher.

Which companies use Anthropic and Fastmail?

Auth57 Labs, Auth57 Labs, draw.io, Sendmarc and SimpleLocalize, and 1 more company. Each one links to the evidence behind it.

How does StrataDB know a company uses Anthropic and Fastmail?

From four kinds of public evidence: subprocessor lists, privacy policies, website code and job postings. Each is kept apart with its source and the date we saw it. A company missing here means we found no evidence, not that it does not use them.

Find every company using Anthropic and Fastmail

See the full list with the source for each company, and run the same lookup for any technology from the API, Claude or your browser.

  • Every company and vendor, with its public source
  • 100 API calls a month, plus MCP and the Chrome extension
  • Work email only. No card, no sales call