MCP for Thunderbird 0.2.2

MCP for Thunderbird 0.2.2 improves the messages AI apps write: lists in the text arrive as real bulleted and numbered lists, and the images in your signature show in the compose window again.

Upgrade

1. Install mcp-for-thunderbird-0.2.2.xpi over the installed add-on (Add-ons and Themes, the gear, "Install Add-on From File…"). Thunderbird asks you to allow one new permission, scripting (see below). Your settings are kept.
2. Install the host for your system from the files below, as for 0.2.1. The host is needed for the new description of the message text, which tells AI apps how to write lists. If the host now lives at another path, run mcp-for-thunderbird setup again so Thunderbird finds it, and mcp-for-thunderbird setup --clients=… again for the AI apps you set up with it.

INSTALL.md has the full steps for each system. The installers and the add-on are not signed.

Changes

• Lists: mail_compose, mail_draft and mail_send take the message text as plain text and turn it into an HTML message. A paragraph whose lines all start with - or * now becomes a bulleted list, and one whose lines start with 1. , 2. and so on becomes a numbered list. An indented line continues the list item above it. A list needs a blank line between it and the text around it; otherwise its lines stay as typed. Before 0.2.2, list lines arrived as typed dashes.
• Signature images: when mail_compose put the text above the signature, Thunderbird rebuilt the window's document and did not load the signature's remote images again, so they showed broken in the window. Sent mail was not affected. The text is now inserted at the top of the open window, and the signature stays as Thunderbird laid it out.
• New permission: scripting, used only to put the text at the top of a compose window the add-on opened. PRIVACY.md lists every permission and what it is used for.

Files

• mcp-for-thunderbird-0.2.2.xpi: the Thunderbird add-on.
• mcp-for-thunderbird-0.2.2-windows-amd64-setup.exe and -windows-arm64-setup.exe: Windows installers.
• mcp-for-thunderbird-0.2.2-macos.pkg: macOS installer.
• .deb packages for Debian and Ubuntu, amd64 and arm64.
• .tar.gz and .zip archives of the host for Linux, macOS and Windows, each with an SPDX bill of materials.
• .mcpb Claude Desktop extensions for macOS and Windows.
• SHA256SUMS: checksums of every file above.

The server is listed in the official MCP Registry as io.github.wadejbeckett/mcp-for-thunderbird.

MCP for Thunderbird 0.2.1

MCP for Thunderbird 0.2.1 is a security update of the host program. The 0.1.0 and 0.2.0 hosts were built with Go 1.25.14, which no longer gets security fixes; 0.2.1 is built with Go 1.26.10. Upgrading the host is recommended for everyone.

Upgrade

1. Install the host for your system from the files below, as for 0.2.0. The Windows installer, the macOS package and the .deb install to a fixed folder and need nothing more. If the host now lives at another path (for example after a package-manager upgrade into a versioned folder), run mcp-for-thunderbird setup again so Thunderbird finds it, and mcp-for-thunderbird setup --clients=… again for the AI apps you set up with it.
2. The add-on is unchanged since 0.2.0 apart from its version number, and the 0.2.0 add-on works with the 0.2.1 host. To keep the two versions matched, install mcp-for-thunderbird-0.2.1.xpi over the installed add-on (Add-ons and Themes, the gear, "Install Add-on From File…"). Your settings are kept.

INSTALL.md has the full steps for each system. The installers and the add-on are not signed.

Security fixes

• Go 1.26.10 fixes ten vulnerabilities in the Go standard library that the host's code can reach: seven in net/http (GO-2026-6603, GO-2026-6605, GO-2026-6610, GO-2026-6611, GO-2026-6612, GO-2026-6613, GO-2026-6617), and one each in crypto/x509 (GO-2026-6809), crypto/tls (GO-2026-6607) and net/textproto (GO-2026-6608). It also fixes four that the host's code does not call (GO-2026-6599, GO-2026-6600, GO-2026-6604, GO-2026-6609). The host accepts connections only from programs on the same computer (127.0.0.1), which narrows who could reach these flaws.
• golang.org/x/sys is updated to 0.47.0, which includes the fix for GO-2026-5024, a flaw in its Windows function NewNTUnicodeString. The host never calls that function.
• Every change is now checked with govulncheck for Linux, Windows and macOS, and the checks fail when the host's code can reach a known Go vulnerability.

Files

• mcp-for-thunderbird-0.2.1.xpi: the Thunderbird add-on.
• mcp-for-thunderbird-0.2.1-windows-amd64-setup.exe and -windows-arm64-setup.exe: Windows installers.
• mcp-for-thunderbird-0.2.1-macos.pkg: macOS installer.
• .deb packages for Debian and Ubuntu, amd64 and arm64.
• .tar.gz and .zip archives of the host for Linux, macOS and Windows, each with an SPDX bill of materials.
• .mcpb Claude Desktop extensions for macOS and Windows.
• SHA256SUMS: checksums of every file above.

The server is listed in the official MCP Registry as io.github.wadejbeckett/mcp-for-thunderbird.

MCP for Thunderbird 0.2.0

MCP for Thunderbird 0.2.0 makes the add-on safer with untrusted mail, fixes archiving, and adds Thunderbird 140 ESR. Upgrading is recommended for everyone on 0.1.0.

Upgrade

1. Install the host for your system from the files below, as for 0.1.0. If your AI apps were set up by setup and the host now lives at another path (for example after a package-manager upgrade), run mcp-for-thunderbird setup again: it replaces the entries it wrote, and leaves entries you edited or wrote yourself alone and reports them.
2. In Thunderbird, install mcp-for-thunderbird-0.2.0.xpi over the old add-on (Add-ons and Themes, the gear, "Install Add-on From File…"). Your settings are kept.

INSTALL.md has the full steps for each system. The installers and the add-on are not signed in this release either.

Safer with untrusted mail

• mail_read now returns the text a reader sees: the HTML part of a message, cleaned, instead of a plain-text alternative the reader never sees. When the plain-text alternative says something the shown text does not, the result says so with plainTextDiffers.
• More hidden text is removed before an AI app sees it: transparent text, text moved off-screen, clipped or scaled to nothing, text drawn in the background colour through -webkit-text-fill-color, link addresses of invisible links and descriptions of invisible images. Text that only a style rule for wide screens shows is no longer dropped by mistake.
• Untrusted text is wrapped in markers that carry a new random code on every call, so a message cannot fake the end of the block; look-alike markers written with fullwidth, mathematical, Cyrillic or Greek letters are defused.
• Every Unicode default-ignorable character is stripped, and contact names and addresses are cleaned like message headers.
• The SPF, DKIM and DMARC summary is read the way RFC 8601 lays the header out: a quoted value can no longer pass itself off as dmarc=pass, and Microsoft 365's headers are read correctly.
• A crafted message can no longer make the add-on's text cleaner run for minutes.

Fixes

• mail_archive works. In 0.1.0 every call failed. It now refuses when Thunderbird could archive into a folder you excluded or into another account.
• A move, draft, send or compose window that times out, is cancelled or loses Thunderbird is reported as possibly done, so an AI app does not repeat it.
• mail_attachment can fetch one of several attachments with the same name: mail_read lists each attachment's part, and mail_attachment accepts it.
• mail_thread lists each message once, also on Gmail, where a message sits in several folders.
• mail_tag no longer loses a change made at the same time.
• The options refuse a drive root or your home folder as the attachment folder, and an entry in the attachment folder that is not an ordinary file, such as a pipe, is refused when attaching.
• Rotating the access key is confirmed, and a refused rotation is reported; the old key never stays valid.
• The host closes idle connections and abandoned sessions, and checks that the program it sends the access key to is really the host.

Thunderbird 140 ESR

Thunderbird 140 ESR, which Debian, Ubuntu and many managed desktops ship, is now supported. On 140, mail_draft and mail_send are not offered, because the interfaces that save or send a message without a window arrived in Thunderbird 153; mail_compose opens a filled-in window instead, and every other tool works as on later versions.

Files

• mcp-for-thunderbird-0.2.0.xpi: the Thunderbird add-on.
• mcp-for-thunderbird-0.2.0-windows-amd64-setup.exe and -windows-arm64-setup.exe: Windows installers.
• mcp-for-thunderbird-0.2.0-macos.pkg: macOS installer.
• .deb packages for Debian and Ubuntu, amd64 and arm64.
• .tar.gz and .zip archives of the host for Linux, macOS and Windows, each with an SPDX bill of materials.
• .mcpb Claude Desktop extensions for macOS and Windows.
• SHA256SUMS: checksums of every file above.

The server is listed in the official MCP Registry as io.github.wadejbeckett/mcp-for-thunderbird.

MCP for Thunderbird 0.1.0

First release of MCP for Thunderbird: a Thunderbird add-on and a small local host that let AI apps (Claude Desktop, Claude Code, Codex, Cursor) read, organise and draft mail through the Model Context Protocol, on your computer only. Nothing goes through an outside server, and with the default settings nothing an AI app does can send mail or delete anything for good.

Install

1. Install the host for your system from the files below. Windows: run the -setup.exe installer. macOS: open the .pkg and install for yourself only. Linux: install the .deb, or unpack the archive, then run mcp-for-thunderbird setup as your own user.
2. In Thunderbird 153 or later, open Add-ons and Themes, choose the gear, then "Install Add-on From File…", and pick mcp-for-thunderbird-0.1.0.xpi. The add-on is not on addons.thunderbird.net yet, so Thunderbird installs it from this file and does not update it by itself.
3. The add-on opens a setup page: choose the accounts AI apps may use, the permission level, and the AI apps to connect.

INSTALL.md has the steps for each system, including the unknown-publisher warnings on Windows and macOS: the installers are not code-signed in this release.

Files

• mcp-for-thunderbird-0.1.0.xpi: the Thunderbird add-on.
• mcp-for-thunderbird-0.1.0-windows-amd64-setup.exe and -windows-arm64-setup.exe: Windows installers (per user, no administrator rights).
• mcp-for-thunderbird-0.1.0-macos.pkg: macOS installer (Intel and Apple silicon).
• .deb packages for Debian and Ubuntu, amd64 and arm64.
• .tar.gz and .zip archives of the host for Linux, macOS and Windows.
• .mcpb Claude Desktop extensions for macOS and Windows, an alternative to the setup page for that app.
• SHA256SUMS: checksums of every file above.

What it does in 0.1.0

• Read: accounts, folders, search (pointers only, never message text), one message at a time, conversations, and attachments saved into a folder you choose.
• Organise: mark, tag, move, archive and move to Trash; nothing is deleted for good.
• Draft: save a message, reply or forward to Drafts, or open a filled-in compose window with your identity's signature for you to check and send.
• Contacts: look people up in your address books (off until you turn it on).
• Sending without a window stays off unless you enable it and list the addresses it may send to.
• Filter suggestions are written out for you to create in Thunderbird; the add-on cannot change filters itself.
• The toolbar button shows the connection state and pauses everything on demand; the options keep an activity log of the last 500 requests.

Known limits

• Linux: Thunderbird from thunderbird.net or a distribution package works; the Snap build is untested and Flatpak is not supported.
• The add-on and the installers are unsigned in this release.
• The host runs only while Thunderbird runs; calendar and tasks are out of reach of add-ons.

Privacy and security details: PRIVACY.md and SECURITY.md.