Why Thunderbird → PDF?
Thunderbird is an excellent mail client but not a great archive format. A profile folder is tied to Thunderbird itself — delete the app, change Macs, or let the profile corrupt, and your mail becomes awkward to access. PDFs are independent, searchable, and durable. Converting Thunderbird mailboxes to PDF is the standard move when you're leaving Thunderbird, archiving old accounts, or handing over years of correspondence for legal review.
Key concept: every Thunderbird folder is a MBOX file
Thunderbird's storage model is simple. Inside your profile folder, every mailbox (Inbox, Sent, a custom folder called "Clients 2024", etc.) is backed by a single MBOX file with no file extension. A companion .msf file sits next to it as the index; Thunderbird regenerates .msf if deleted, so you can ignore it.
This matters because converting Thunderbird to PDF is really just converting each of those MBOX files to PDF. No special export step required.
Step 1 — Find your Thunderbird profile folder
On Mac, Thunderbird profiles live at:
~/Library/Thunderbird/Profiles/To get there quickly:
- In Finder, press Cmd + Shift + G (Go to Folder).
- Paste the path above and hit Return.
- You'll see one or more folders with random names ending in
.default,.default-release, or.default-esr. That's your profile.
Alternative: inside Thunderbird, go to Help → Troubleshooting Information, then click Show in Finder next to "Profile Directory". Opens the profile folder directly.
Step 2 — Locate the MBOX files
Inside the profile, your mail lives in two places:
Local Folders (on-disk, never synced)
~/Library/Thunderbird/Profiles/<profile>.default/Mail/Local Folders/This contains files like Inbox, Sent, Drafts, plus any custom folders you created under Local Folders. These are all MBOX files — just without the .mbox extension.
Mail accounts (IMAP, POP)
Each mail account has its own directory:
~/Library/Thunderbird/Profiles/<profile>.default/ImapMail/<account-host>/
~/Library/Thunderbird/Profiles/<profile>.default/Mail/<account>/Inside each you'll find the same extensionless files, one per mailbox folder. For IMAP accounts, these are cached copies of what's on the server.
Step 3 — Copy the MBOX files out
Don't convert directly from the profile folder. Thunderbird may hold locks or write to those files while running, and conversion tools can misread partial writes.
Copy the specific mailboxes you want to a working folder — ~/Desktop/Thunderbird-Export/ works fine. If you want to keep the original folder structure:
Thunderbird-Export/
├── Local Folders/
│ ├── Inbox
│ ├── Sent
│ └── Archive 2024
└── Work Account/
├── INBOX
└── SentIf the files have no extension, Finder shows them as "document" files. That's fine — MBOX to PDF identifies them by content, not filename.
Step 4 — Import into MBOX to PDF
Install MBOX to PDF from the Mac App Store. Drag a single MBOX file (or several) into the window.
If drag-and-drop doesn't work because the file has no extension, use the in-app file picker — it doesn't filter by extension.
Converting multiple folders
To preserve the folder-per-folder structure in the output:
- Convert each MBOX file in its own run.
- Output to a folder matching the source folder name (e.g.
Sent.pdforSent/containing one-PDF-per-email). - Build the same hierarchy in Finder afterward.
For a single combined archive (all folders merged), drag all MBOX files in at once. MBOX to PDF treats them as one combined dataset — messages from Inbox, Sent, and Archive show up in the same list and convert into a single PDF set. You lose the folder boundaries but gain a unified chronological archive.
Step 5 — Configure and export
Recommended settings depending on why you're archiving:
Leaving Thunderbird for another client
- One PDF per email, so individual messages are searchable in Finder.
- Extract attachments to a sibling folder.
- Filename pattern: date + subject.
Handing a mailbox to legal
- Combined PDF with sequential pagination.
- Page numbers, document title header, "Confidential" watermark.
- Extract attachments to a sibling folder.
- Leave quoted replies intact.
Personal archive
- One PDF per email or combined, your preference.
- Strip quoted replies for cleaner individual messages.
- Optional black-and-white mode if you plan to print.
Common gotchas
"I can't find the profile folder because ~/Library is hidden"
In Finder, press Cmd + Shift + . (period) to toggle hidden files. Or use Go → Go to Folder (Cmd + Shift + G) and paste the path directly.
"There are multiple profiles"
If you've had Thunderbird for years, you may have multiple .default folders. The one currently in use has the latest modification date. Open Help → Troubleshooting Information → Profile Directory to confirm the active one.
"My folder has a .msf file — do I need it?"
No. .msf files are Thunderbird's per-folder index. Ignore them. Only copy the extensionless MBOX file.
"The MBOX file is enormous"
Thunderbird doesn't compact folders automatically. Large folders accumulate deleted-but-not-purged messages. Before converting, you can compact the folder in Thunderbird (File → Compact on the folder) to strip deleted messages from the file. This is optional — MBOX to PDF ignores deleted-marker headers automatically.
"I'm seeing duplicate messages"
If you converted both Local Folders and an IMAP account's cached folders, and you had saved mail from IMAP into Local Folders, you'll see duplicates. Convert one or the other, not both.
Advanced: converting an entire profile at once
If you want the whole profile converted to a single archive without preserving folder structure:
- Find every MBOX file under the profile's
Mail/andImapMail/directories. In Terminal:find ~/Library/Thunderbird/Profiles -type f ! -name "*.msf" ! -name "*.sbd" ! -name "*.dat"— lists candidate MBOX files. - Copy them all to one working folder.
- Drag the whole folder into MBOX to PDF.
For most users this is overkill; converting the specific folders you care about is faster and produces cleaner output.
Frequently asked questions
Where does Thunderbird store emails on Mac?
In ~/Library/Thunderbird/Profiles/. Each mailbox folder is an MBOX file without a file extension.
Why don't Thunderbird's mail files have extensions?
Convention inherited from Unix mail. The file contains pure MBOX data; the absence of an extension means no default app tries to open it.
Can I convert Thunderbird folders without quitting Thunderbird?
Yes, but safer to copy the MBOX files out first. Live Thunderbird may lock files. When in doubt, quit Thunderbird.
Does Thunderbird have a built-in PDF export?
Only one email at a time via print-to-PDF. No built-in batch export. The ImportExportTools NG add-on adds bulk export but with limited formatting.
Will my folder hierarchy be preserved in the PDFs?
Not automatically — convert each folder's MBOX separately and replicate the hierarchy in Finder.
How do I handle Thunderbird's local folders vs IMAP folders?
Both are MBOX. Local Folders are safe to convert anytime. For IMAP caches, quit Thunderbird first to avoid conflicts with live syncing.