- Is it really free?
- Yes. ContinuMail Converter is free and open-source under GPL-3.0, and it stays that way.
- Is my email uploaded anywhere?
- No. Conversion happens entirely on your machine. The app makes no network connections, so nothing is ever uploaded, and it only ever reads your original files.
- Do I need Outlook installed to convert?
- No. ContinuMail writes the PST directly with its own engine, so Outlook does not need to be installed or running to convert. You will, of course, open the finished PST in Outlook afterwards.
- Can Outlook open an mbox file directly?
- No. Outlook cannot read the mbox format and has no "import mbox" option, so you cannot open an .mbox file in Outlook on its own. The way to get mbox mail into Outlook is to convert it to a PST file first, which is the native format Outlook uses. ContinuMail does that conversion for free, on your own PC.
- What does it preserve?
- Folder structure, attachments (including inline images and embedded .eml), HTML bodies with a plain-text fallback, To/Cc/Bcc, read/unread state, importance, and threading headers. When you convert a live Thunderbird profile it also brings across tags, stars, replied/forwarded marks and junk state — plus your calendars, contacts (photos included) and tasks. What is preserved, and what is not, is documented field by field on the What gets converted page.
- Can it convert a whole Thunderbird profile?
- Yes. Point it at your Thunderbird profile and it auto-discovers every mail account and local archive, mirrors the full folder tree, and converts each account into its own PST (or one combined file) — with that account's calendars, contacts and tasks routed into the same PST. This is where the extra per-message detail like tags and flags comes from, because that information lives in the profile rather than in a bare exported mbox.
- Do my Thunderbird tags become Outlook categories?
- Yes. From a live Thunderbird profile, your tags become Outlook categories under their real names, with their colours written straight into the PST — no Outlook automation, no separate step. One caveat: classic Outlook only renders category colours when the PST is your primary/default data store; opened as a secondary data file, categories show their names but not their colours. Stars become follow-up flags, and replied/forwarded marks carry over too.
- Can it handle very large archives?
- Yes. It can split output into multiple PST files by size, and large attachments spill to disk so memory stays manageable.
- Is the installer code-signed?
- Not yet. This is an early 0.x release, so Windows SmartScreen may warn about an unknown publisher. Code signing is on the roadmap. See the download page for what to expect.
- Which sources and formats are supported?
- Right now it converts Thunderbird profiles and mbox archives to Outlook PST, and that is the only conversion it does today. mbox is what programs like Thunderbird and Gmail Takeout export, and those are the sources it has been tested against so far. From a Thunderbird profile it also converts calendars, contacts and tasks. Other input formats — EML, MSG, Apple Mail — are on the roadmap, but not supported yet.
- Is there a Mac or Linux version?
- The desktop app is Windows 10/11 today. The command-line converter runs on Windows, Linux x64 and macOS (Apple Silicon) — grab the binary for your OS from the releases page on GitHub. A cross-platform desktop app is on the roadmap.