Using Thunderbird as an email archive vs EmailAttic

By Michael, founder of EmailAttic · October 2026 · 5 min read

Thunderbird is free, open source, runs everywhere, and it will happily hold twenty years of mail. A lot of people use it as their archive. It is a reasonable choice, and it is a different job from the one EmailAttic does, so the question is which job you have.

What Thunderbird is

A mail client. It connects to accounts, downloads mail, and stores it in standard MBOX or Maildir files inside its profile. Its global search is fast, its folder handling is mature, and with the ImportExportTools NG add-on it will import loose MBOX and EML files into Local Folders. If you want one program in which to read and search everything you have ever kept, it does that well, for free, on Windows, macOS and Linux.

Where it struggles as an archive

• Old Outlook files. Thunderbird has no native PST or OST reader. Its Outlook import on Windows works through Outlook itself, so it needs a working Outlook installation and an account that can open the file. A drawer of PSTs from dead machines is exactly the case it cannot handle.
• Duplicates. Import three backups that overlap and you have three copies of most messages. Thunderbird keeps what you give it; removing duplicates means an add-on and a manual pass per folder.
• Who the mail belonged to. Thunderbird organizes by account and the folders you make. Mail recovered from five old accounts and a Takeout export arrives as one pile unless you sort it by hand.
• Nothing was lost? There is no report. When you want to delete the old drives, you are trusting that the import got everything.

What EmailAttic does instead

EmailAttic is not a mail client and does not try to be. You point it at the folders, drives and backup files, and it reads Outlook PST and OST, MBOX, EML, MSG, Maildir and Google Takeout, including inside nested zips. It compares message content rather than filenames, keeps one copy of each message, works out which mailbox each file belonged to and files the messages per person. The output is ordinary message files in ordinary folders, and every run ends with a plain-language report of what was read, what was kept, what was a duplicate and what could not be opened.

They work well together

The two are not rivals. The sensible setup for a messy backlog is EmailAttic first, Thunderbird second: let EmailAttic reconcile the backups into one de-duplicated archive filed by person, then point Thunderbird at that archive to read and search it. You get Thunderbird's search on a clean, complete, accounted-for set of mail, instead of on three overlapping imports.

What about the price?

Thunderbird is free. EmailAttic is a one-time $59.99 with a free trial that never expires. What you are paying for is the part Thunderbird does not do: reading the Outlook files without Outlook, the message-level de-duplication, the per-person filing, and the report that lets you finally retire the old drives.

Questions people ask

Can Thunderbird open a PST file?

Not on its own. Thunderbird's Outlook import uses Outlook itself, so it needs Outlook installed and able to open the file. For PST files from old machines without Outlook you need a tool that reads PST directly, which EmailAttic does.

Can I use Thunderbird to read EmailAttic's archive?

Yes. EmailAttic writes standard message files in ordinary folders, so Thunderbird can import them with ImportExportTools NG, and any other mail client or search tool can read them too.

Does Thunderbird remove duplicate emails?

Not by itself. The Remove Duplicate Messages add-on can do it folder by folder. EmailAttic removes duplicates across every source by comparing message content before anything is written.