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Postfleet is inbound email infrastructure for AI agents, built on the assumption that any message can be an attack.
Every message runs the same pipeline before your agent sees it: SPF/DKIM/DMARC checks, HTML-to-text cleaning, removal of hidden elements, HTML comments and zero-width characters, malware and spam screening, then a prompt-injection scan. What comes out is typed JSON matching a schema you define.
It fails closed. Malware is quarantined, spam is suppressed, and a message flagged for injection risk never reaches extraction โ your agent gets an explicit status (skippedinjectionrisk) instead of quietly poisoned context. The pre-sanitization body is never sent to agent-facing tools.
Connect over MCP with 14 tools (Claude, Claude Code, Cursor, Windsurf, Cline, VS Code) or use the REST API. Sends are idempotent โ retry with the same client_id and the email goes out at most once โ with optional human approval before anything irreversible leaves.
We publish the red-team scoreboard, including what got through and one false flag we caught ourselves: 99.1% of 113 attacks caught, most written by independent models and a public benchmark rather than by us. Screened against known patterns, never claimed immune.
Free: 100 messages, 3 mailboxes. Sanitization and injection screening are never metered.
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Postfleet's answer:
It treats an agent's inbox as a trust boundary, not a pipe. Every inbound email is screened for prompt injection, stripped of hidden text, and turned into structured JSON before the agent ever reads it. The unusual part: I red-team the filter with rival models and publish the whole scoreboard, catches and misses both. Screened, never immune.
Postfleet's answer:
Most email APIs for agents hand you the raw body and leave defense to your app layer. Postfleet screens first and fails closed, so flagged mail reaches the agent as inert data instead of trusted content. It's backed by an injection guarantee and a public red-team scoreboard, so the security claim comes with receipts rather than a marketing number.
Postfleet's answer:
Developers building AI agents that receive email: indie hackers, agent-framework builders, and small platform teams wiring an agent to an inbox. People who've read at least one prompt-injection horror story and would rather see published results than take a claim on faith.
Postfleet's answer:
I've spent 18 years building software, the last 6 as an architect drawing trust boundaries between systems that shouldn't blindly trust each other. When I watched people give AI agents email inboxes, I saw the boundary everyone skipped: anyone who can email an agent can drop instructions into its context. Postfleet is that missing boundary.
Postfleet's answer:
Next.js, TypeScript, and Supabase (Postgres), deployed on Vercel. An MCP server so an agent can sign itself up. Anthropic models run the injection scan and schema extraction, Resend/SES handles inbound mail, and ClamAV scans attachments.
Protonmail is the best secure email solution period, other products in the suite such as ProtonVPN and hopefully soon Drive and Calendar will finally make it the perfect Gsuite alternative.
Based on our record, ProtonMail seems to be more popular. It has been mentiond 414 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
You might want to consider getting a domain name of your own and then get email hosting which will allow you to set up your email in the way you want. If you don't want to have to manage and pay for domain name and email hosting, you may try premium email services like Space Email, Proton Mail etc. With then you'll definitely be able to get a username/email address of your choice. Source: over 2 years ago
I closed all Proton Mail tabs and navigated to protonmail.com and a cleared out login area was shown. Without checking the "keep me logged in", I entered my credentials and was prompted for my 2FA info. I entered that and it worked. Source: almost 3 years ago
Can I add my gmail account to my proton mail account so I can send emails and choose betwen my gmail.com email or my protonmail.com email account? Im not talking about the easy switch feature btw. Source: almost 3 years ago
I hear ProtonMail[1] is good, especially for your needs. [1]: https://protonmail.com/. - Source: Hacker News / about 3 years ago
Protonmail.com for my primary, though really, simplelogin.com when I sign up at a site. Source: about 3 years ago
Tutanota - Get your encrypted mailbox for free.
Nylas Mail - The Nylas Cloud API powers your application with email, calendar & contacts features. Built-in features for better email, calendar, and contact management.
Gmail - Gmail is available across all your devices Android, iOS, and desktop devices. Sort, collaborate or call a friend without leaving your inbox.
Evolution - Apps/Evolution - GNOME Wiki!
Zoho Mail - Zoho Mail is a secure, encrypted, and enterprise-ready email solution, a suite of apps tailor-made for your organization's needs.
Mailbird - Mailbird is the best email client for Windows 7, 8 and 10