Fastmail

Install as a Claude Desktop Extension (DXT)

You can install this server as a Desktop Extension for Claude Desktop using the packaged.dxtfile.

npm run build npx @anthropic-ai/dxt pack

This producesfastmail-mcp.dxtin the project root.

- Open the.dxtfile, or drag it into Claude Desktop
- When prompted:

Use any of the tools (e.g.get_recent_emails).

Response shape for list/search tools:the query tools (list_emails,list_emails_metadata,search_emails,search_emails_metadata,get_recent_emails,advanced_search,advanced_search_metadata,list_contacts,search_contacts) return a{"total", "items"}JSON envelope —totalis the server-reported match count,itemsthe returned page. When the server reports no total, a bare array is returned.

- check_function_availability: Check what's available and get setup guidance
- test_bulk_operations: Safely test bulk operations with dry-run mode
- send_email: Full-featured email sending with proper draft/sent handling
- advanced_search: Powerful multi-criteria email filtering
- get_recent_emails: Quick access to recent emails from any mailbox

- list_mailboxes: Get all mailboxes in your account. On accounts with many mailboxes the full output can be large — passpropertiesfor a slim view.

- Parameters:properties(optional array of fields to return),parentId(optional; only children of this mailbox,nullfor top level)

- Parameters:name(required),parentId(optional, omit or null for top level)

- Parameters:mailboxId(optional),limit(default: 20, max: 100),ascending(optional, oldest first)

- Parameters:mailboxId(optional),limit(default: 20, max: 100),ascending(optional, oldest first)

- Parameters:emailId(required),to,cc,bcc,from,subject,textBody,htmlBody,replyTo,attachments(all optional)

- Parameters:query(required),limit(default: 20, max: 100),ascending(optional, oldest first),excludeDrafts(optional, omit draft messages)
- Drafts areincluded by default. SetexcludeDrafts: trueto filter them out server-side.
- Searchesall mailboxes including Trash and Spam. For cleanup/verification flows, exclude the Trash mailbox explicitly (e.g.advanced_searchwithexcludeMailboxIds) rather than trusting a bare search count.

- Parameters:limit(default: 10, max: 50),mailboxName(optional),ascending(optional, oldest first)
- WhenmailboxNameis omitted, all mailboxes are searchedexcept Trash and Spam. Pass a mailbox name (e.g.'inbox','sent') to scope to one folder.

- Parameters:query(required),limit(default: 20, max: 100),ascending(optional, oldest first)

- Parameters:emailId(required),read(default: true)

- Parameters:emailId(required),pinned(default: true)

- Parameters:emailId(required),targetMailboxId(required)

- Parameters:emailId(required),targetMailboxId(required)

- Parameters:emailId(required),mailboxIds(required array)

- Parameters:emailId(required),mailboxIds(required array)

- get_email_attachments: Get list of attachments for an email

- Parameters:emailId(required)

- Parameters:emailId(required),attachmentId(required),savePath(optional)
- savePathmay be absolute or relative. Relative paths (including a bare filename) resolve against the download directory, so an attachment lands there in one step. Absolute paths must fall within that directory; traversal or symlink escape outside it is rejected. To save directly into your own location, setFASTMAIL_DOWNLOAD_DIRto that root — confinement stays on, scoped to the directory you choose.

- Parameters:emailId(required),attachmentId(required),remotePath(required, relative),overwrite(default false),createParents(default true)
- The storage server and credentials come fromFASTMAIL_WEBDAV_*env config; the tool only chooses the relative path beneath that base. Existing files are never replaced unlessoverwrite: true.

- Parameters:query(optional),from(optional),to(optional),subject(optional),hasAttachment(optional),isUnread(optional),isPinned(optional),mailboxId(optional),requiredMailboxIds(optional array — email must be in ALL of these),excludeMailboxIds(optional array — exclude emails in any of these),after(optional),before(optional),limit(default: 50, max: 100),ascending(optional, oldest first)
- Likesearch_emails, searchesall mailboxes including Trash and Spam— scope withmailboxId/excludeMailboxIdswhen that matters. (get_recent_emailsis the one that excludes Trash/Spam by default.)

- Parameters:threadId(required),includeDrafts(optional, include in-progress drafts)
- Draft messages areexcluded by default(an in-progress reply is noise when reading a conversation). SetincludeDrafts: trueto include them. Drafts are identified by the$draftkeyword, so the asymmetry withsearch_emails(which includes drafts by default) is deliberate: a search should still find everything you've written.

- Parameters:threadId(required),includeDrafts(optional)

- get_mailbox_stats: Get statistics for a mailbox (unread count, total emails, etc.)

- Parameters:mailboxId(optional, defaults to all mailboxes)

- bulk_mark_read: Mark multiple emails as read/unread

- Parameters:emailIds(required array),read(default: true)

- Parameters:emailIds(required array),pinned(default: true)

- Parameters:emailIds(required array),targetMailboxId(required)

- Parameters:emailIds(required array),mailboxIds(required array)

- Parameters:emailIds(required array),mailboxIds(required array)

- list_contacts: List all contacts

- Parameters:limit(default: 50, max: 200)

- Parameters:query(required),limit(default: 20, max: 100)

- Recent emails retrieval (based on top-ten example)
- Email management operations
- Efficient chained JMAP method calls

The server uses bearer token authentication with Fastmail's API. API tokens provide secure access without exposing your main account password.

Fastmail applies rate limits to API requests. The server handles standard rate limiting, but excessive requests may be throttled.

However, Fastmail fully supportsCalDAVfor calendar access viacaldav.fastmail.com. All calendar tools use CalDAV directly.
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Create an app-specific password on Fastmail:

- Go toSettings → Privacy & Security → Manage app passwords
- Create a new app password (you can name it "CalDAV MCP" or similar)

Set the following environment variables:

export FASTMAIL_CALDAV_USERNAME="your-email@fastmail.com" export FASTMAIL_CALDAV_PASSWORD="your-app-specific-password" # Optional: display name for ORGANIZER when creating events with participants export FASTMAIL_CALDAV_DISPLAY_NAME="Your Name"

When these variables are set, all calendar tools are available. When they are not set, calendar tools will return an error with setup instructions.

save_attachment_to_webdavsaves attachments straight to cloud storage. Configure the target (never supplied by tools at runtime — this is deliberate, so a misbehaving caller cannot redirect uploads):

# Fastmail Files: export FASTMAIL_WEBDAV_URL="https://myfiles.fastmail.com/" export FASTMAIL_WEBDAV_USERNAME="your-email@fastmail.com" export FASTMAIL_WEBDAV_PASSWORD="app-password-with-files-scope" # ...or any WebDAV server, e.g. Nextcloud: # export FASTMAIL_WEBDAV_URL="https://cloud.example.com/remote.php/dav/files/USERNAME/"

The URL must be HTTPS. Note: Fastmail Files ignores the WebDAVIf-None-Matchprecondition, so the tool performs an explicit existence check before non-overwrite uploads.

send_email,create_draft,edit_draft, andreply_emailaccept anattachmentsarray. Each entry uses exactly one source:

- { "localPath": "report.pdf" }— a file insideFASTMAIL_DOWNLOAD_DIR(same confinement as downloads)
- { "emailId": "...", "attachmentId": "..." }— re-attach from an existing email (zero-copy: no bytes are transferred)
- { "blobId": "...", "name": "...", "type": "..." }— an already-uploaded JMAP blob

Uploads respect the server'smaxSizeUpload(~50 MB on Fastmail). Editing a draft preserves its existing attachments.