MsgLens MCP server

MsgLens — a .msg / .eml / winmail.dat viewer that never uploads your files

A browser-based viewer for Outlook .msg, standard .eml and winmail.dat (TNEF) email files. Everything — container parsing, RTF decompression, HTML sanitisation, ZIP creation, PDF export — runs client-side. There is no backend, which is what makes "your file is never uploaded" a structural fact rather than a promise.

Why this exists

Checked against the three tools that rank for this query, 30 September 2026, by reading their pages and upload code (no file was uploaded):

So the "they all upload it" line is not true, and this README used to say it was. One of the three is genuinely local. The same comparison, kept current, is on the site at /msg-viewer-comparison/.

What is left is a real split. Against the two hosted converters, the argument is that business email should not be posted to an unknown server to be read. Against the local one, it is the other formats: .eml and winmail.dat.

The technical claim underneath all of it: Outlook usually stores the body only as compressed RTF with the original HTML encapsulated inside it ([MS-OXRTFEX]). Against a corpus of 20 real business .msg files, 17 were RTF-only — a viewer that reads PidTagHtml and gives up renders nothing for 85% of them. That number is measured. Whether any particular competitor handles that case is not tested here, and saying otherwise would need uploading a message to them to find out.

winmail.dat used to be the one thing encryptomatic did that this did not. It now reads those too — see below.

What it does

than extension, so a renamed file still opens.

• Reads .msg, .eml and winmail.dat, detected by magic bytes rather

in Rich Text and the receiving server could not unpack it. The formatted body and every real attachment are trapped inside it; this pulls them back out. Note that TNEF carries the sender but not the recipient list — those stayed in the carrying message's own headers, which the file does not contain, so To/Cc show as empty rather than guessed.

• Unpacks winmail.dat (TNEF) — the file people receive when Outlook sent

PidTagBodyHtml → de-encapsulated PidTagRtfCompressed → PidTagBody.

• Recovers the body through the full fallback chain — PidTagHtml →

, not inline attributes; a viewer that keeps only the body fragment silently drops table borders, fonts and colours from most real mail.

• Resolves cid: inline images against the message's own attachments.
• Keeps the message's own stylesheets. Outlook writes formatting into

tracking pixel, with a per-message opt-in.

• Blocks remote images by default so opening a message cannot fire a

PidTagInternetCodepage instead of assuming UTF-8.

• Decodes non-Latin bodies using the code page declared in

attachments in place.

• Extracts attachments individually or as a ZIP; opens embedded .msg

rather than printing the app, because iframe content cannot paginate across printed pages — printing the page directly clips anything over one sheet.

• Exports to .eml, .txt and PDF. Printing opens a dedicated print document

• Shows raw internet headers — for IT, deliverability and discovery work.
• Multi-file, keyboard-navigable, dark mode, English + Traditional Chinese.

Architecture

Shortened. The full README is on GitHub.