Sales Fastmail

Fastmail Platform Help

Helps with everything related to using Fastmail — the independent, privacy-respecting email service with a full JMAP API, custom domains, Masked Email aliases, and integrated calendar/contacts/files. 20+ years independent, no ads, standards-first.

Step 1 — Gather context

If references/learnings.md exists, read it first for accumulated platform knowledge.

Ask the user:

1. What are you trying to do with Fastmail?

   • A) Evaluating Fastmail — is it right for me?
   • B) Migrating from Gmail/Outlook/another provider
   • C) Building with the JMAP API (read, send, search, masked email)
   • D) Comparing Fastmail to alternatives (Proton Mail, Hey, Gmail)
   • E) Setting up custom domains, aliases, or Masked Email
   • F) Troubleshooting sync, calendar, or search issues
   • G) Connecting the MCP server to Claude Desktop
   • H) Something else — describe it

2. Which plan are you on (or considering)?

   • A) Individual (~$5/mo — 60 GB, custom domains, Masked Email)
   • B) Duo (~$8/mo — 2 people, shared calendars)
   • C) Family (~$11/mo — 6 people, 360 GB)
   • D) Business Basic (~$3/user/mo — 6 GB, shared email)
   • E) Business Standard (~$5/user/mo — 60 GB, custom domains)
   • F) Business Professional (~$9/user/mo — 150 GB, retention archive)
   • G) Not sure yet

If the user's request already provides most of this context, skip directly to the relevant step.

Step 2 — Route or answer directly

When routing to another skill, provide the exact command.

If the question is about Fastmail itself, continue to Step 3.

Step 3 — Fastmail platform reference

Read references/platform-guide.md for the full platform reference — capabilities, pricing, JMAP API quick-start, migration, MCP server setup.

Read references/fastmail-api-reference.md for detailed API documentation — authentication, endpoints, OAuth flow, Masked Email methods.

Answer the user's question using only the relevant section. Don't dump the full reference.

Step 4 — Actionable guidance

Focus on the user's specific situation:

• Evaluating Fastmail: Match their priorities. If they need E2E encryption, Proton is better. If they need API access and speed, Fastmail excels. If they need AI, neither — suggest Superhuman or Shortwave.
• Migration: Use the built-in import tool for Gmail/Outlook. Warn about re-training contacts to use new address.
• JMAP API: Start with API token auth (simplest). Use OAuth 2.0 with PKCE for production apps. Session endpoint returns all account info.
• Masked Email: Rate limits apply on creation. Use for signups, newsletters, vendor forms. Integrates natively with 1Password and Bitwarden.
• MCP server: Community-built (jmhron/FastMailMCP). Requires API token. 7 tools for mailbox management, email search, reading, and sending.

If you discover a gotcha or tip not covered in references/learnings.md, append it there.

Gotchas

Best-effort from research — review these, especially items about pricing and plan features that may change.

• No native Zapier/Make integration. Unlike many SaaS tools, Fastmail has no official Zapier or Make connector. Automate via JMAP API directly, IMAP polling, or webhook workarounds.
• Calendar JMAP not yet available. Calendar is CalDAV-only. JMAP calendar support is planned but not shipped yet. Contacts work via both JMAP and CardDAV.
• Price increases. Fastmail raised prices ~40% in late 2025. Current EUR pricing may differ from older USD references you find online.
• Android app reported as weak. The web app and iOS are well-regarded; Android has received complaints about UX quality.
• No AI features. Unlike Superhuman or Shortwave, Fastmail has no AI drafting, categorization, or smart inbox. It's a traditional email client with excellent API access.
• MCP server is community-built. The FastMailMCP server is not official. It works well but may lag behind API changes.
• Self-improving: If you discover something not covered here, append it to references/learnings.md with today's date.

Related skills

• /sales-proton-mail — Proton Mail privacy-first encrypted email (E2E encryption, zero-access, no API). Install: npx skills add sales-skills/sales --skill sales-proton-mail -a claude-code
• /sales-hey — Hey opinionated email service (Screener, Imbox/Feed/Paper Trail, $99/yr). Install: npx skills add sales-skills/sales --skill sales-hey -a claude-code
• /sales-superhuman — Superhuman fastest AI email client (Split Inbox, AI Write, MCP server, $25-40/mo). Install: npx skills add sales-skills/sales --skill sales-superhuman -a claude-code
• /sales-shortwave — Shortwave AI-native Gmail client (AI filters, Ghostwriter, MCP consumer, $24-100/mo). Install: npx skills add sales-skills/sales --skill sales-shortwave -a claude-code
• /sales-em-client — eM Client desktop email client (PGP, calendar/tasks, works with Fastmail via IMAP). Install: npx skills add sales-skills/sales --skill sales-em-client -a claude-code
• /sales-spark-mail — Spark Mail cross-platform AI email client (works with Fastmail via IMAP). Install: npx skills add sales-skills/sales --skill sales-spark-mail -a claude-code
• /sales-sanebox — SaneBox server-side email filtering (works with Fastmail). Install: npx skills add sales-skills/sales --skill sales-sanebox -a claude-code
• /sales-clean-email — Clean Email inbox cleanup (works with any IMAP provider including Fastmail). Install: npx skills add sales-skills/sales --skill sales-clean-email -a claude-code
• /sales-do — Not sure which skill to use? The router matches any sales objective to the right skill. Install: npx skills add sales-skills/sales --skill sales-do -a claude-code

Examples

Example 1: Query emails via JMAP API

User says: "How do I search for emails from a specific sender using the Fastmail JMAP API?" Skill does:

1. Reads API reference for JMAP authentication and Email/query method
2. Shows: get API token from Settings → Privacy & Security → Manage API tokens
3. Provides working cURL example: POST to apiUrl with Email/query + filter by from field
4. Explains result references: chain Email/query → Email/get to fetch full message properties
5. Notes: use properties parameter to limit returned fields for performance Result: Working API example with auth and query chain

Example 2: Should I use Fastmail or Proton Mail?

User says: "I'm a solopreneur choosing between Fastmail and Proton Mail. I need custom domain email and might want to automate things." Skill does:

1. Compares: Fastmail has full JMAP API, OAuth 2.0, MCP server; Proton has no API at all
2. Notes: Proton offers E2E encryption; Fastmail uses TLS + AES at rest (strong but not E2E)
3. Pricing: comparable — Fastmail Individual ~$5/mo vs Proton Mail Plus ~$4/mo for custom domain
4. Key decision: if automation/API matters, Fastmail wins decisively. If E2E encryption is top priority, Proton wins.
5. Neither has AI features — for AI email, suggest Superhuman or Shortwave Result: Clear decision framework based on API needs vs encryption priority

Example 3: Set up Masked Email with 1Password

User says: "How do I use Fastmail's Masked Email feature with 1Password to generate unique email addresses for each service?" Skill does:

1. Reads platform guide for Masked Email section
2. Explains: in 1Password, when creating a new login, click the email field → "Generate Masked Email"
3. Notes: requires Fastmail Individual+ plan and 1Password connected via Settings → Privacy & Security
4. Warns about rate limits on Masked Email creation via API
5. Tip: use forDomain to track which service each alias belongs to Result: Step-by-step 1Password integration with rate limit awareness

Troubleshooting

JMAP API returns 401 Unauthorized

Symptom: API calls fail with 401 even though you have a token Cause: Token may be expired, revoked, or missing the required scope. API tokens and app passwords are different — API tokens work with JMAP, app passwords work with IMAP/SMTP. Solution: 1) Verify you're using an API token (not app password) for JMAP. 2) Check token has required scopes (at minimum urn:ietf:params:jmap:core). 3) Use Authorization: Bearer {token} header. 4) If using OAuth, check if access token expired and refresh via /oauth/refresh.

Calendar not syncing with Google Calendar

Symptom: Events added in Fastmail don't appear in Google Calendar or vice versa Cause: Fastmail calendar uses CalDAV, not a direct Google sync. Two-way sync requires subscribing to each other's calendar URLs. Solution: 1) In Fastmail, go to Calendars → Subscribe → paste your Google Calendar ICS URL. 2) In Google Calendar, go to Other calendars → From URL → paste your Fastmail CalDAV URL. 3) Note: this is read-only subscription sync, not true two-way sync. For full sync, use a bridge like CalDAV-to-Google tools.

Masked Email creation fails with rate limit error

Symptom: MaskedEmail/set returns rateLimit SetError Cause: Fastmail rate-limits Masked Email creation to prevent abuse. Creating many aliases in quick succession triggers this. Solution: 1) Wait and retry — rate limits reset after a cooling period. 2) Batch creations with delays between them. 3) If building an integration, implement exponential backoff on rateLimit errors.