Using Thunderbird

Thunderbird is a popular full featured open source mail client.

On Linux, use your distribution’s package manager to fetch and install Thunderbird.

On Windows, download either the regular or ESR version. The Mozilla project strongly recommends the former, but many users I know just as strongly prefer the latter. Double click to install. There is no official MSI installer for Thunderbird, making it less than ideal for enterprise use.

Upon first run, the mail account setup wizard is run. The wizard will attempt to guess working settings, but my experience is that it’s more reliable to cancel the wizard and enter the settings directly.

Thunderbird’s main configuration settings are found at Menu Button – Preferences – Preferences. While the default settings are appropriate for many users, I like to change:

  • Display – Advanced – Reading: Automatically mark messages as read after displaying for 3 seconds.
  • Composition – Addressing – Automatically add outgoing e-mail addresses to my address books: Disable.
  • Composition – Spelling – Languages: Enable spell check as you type, and download more dictionaries as needed.
  • Privacy – Web Content – Accept cookies: Disable. What is a mail client doing running its own web browser, anyway?
  • Privacy – Web Content – Tell web sites I do not want to be tracked: Enable, not that it does any good.
  • Security – Junk: Disable all. Spam filtering is best done on the server, not on the client.
  • Security – Email Scams: Disable detection. All I’ve ever gotten from this feature are false positives.
  • Security – Antivirus – Allow antivirus clients to quarantine messages: Enable on Windows; disable otherwise.
  • Advanced – General – Return Receipts – When I receive a request for a return receipt: Ask me in all cases.

Per-account configurations are found at Menu Button – Preferences – Account Settings. On each account I like to change:

  • Top level of account configuration – Signature text: As desired. An RFC 3676 compliant separator line is added automatically, so you don’t have to add it here.
  • Server Settings – Server Settings: Check for new messages at startup and every 10 minutes thereafter.
  • Server Settings – Server Settings: When I delete a message, move it to the account’s existing trash folder. Double check that the folder you want is selected.
  • Copies & Folders – When sending messages, automatically place a copy in the account’s existing Sent folder. Double check that the folder you want is selected.
  • Copies & Folders – Message Archives: Disable.
  • Copies & Folders – Drafts: Keep message drafts in the local Drafts folder. This allows you to draft messages off-line. Double check that the folder you want is selected.
  • Composition & Addressing – Composition – Compose messages in HTML: Disable.
  • Composition & Addressing – Composition – Quote the original message when replying, then start my reply below the quote.
  • Junk Settings – Selection – Enable: Disable. As noted above, spam filtering should be done on the server, not on the client.
  • Junk Settings – Selection – Trust junk mail headers: As appropriate. I run Spamassassin on my mail server, so I enable this option for Spamassassin headers.
  • Synchronization & Storage – Message Synchronizing: Enable. Under the “Advanced” button, select all folders except trash, spam, and drafts.

Ideally, change at least the default folders as noted above before using the account. Otherwise, Thunderbird may create duplicate Drafts, Junk, Sent, and Trash folders in the account. To avoid confusion later, I suggest they be deleted.

I find it difficult to coax Thunderbird to set up folders as I like, so once I’ve done the above I check my work. I write a message to myself and save it as draft, confirming that the draft is saved to the desired folder. I then send the message, and confirm that it is removed from the draft folder and appears in the inbox and desired sent folder. I then delete it from the inbox, and confirm that it is moved to the desired trash folder.

If you have address books to import, do it at Tools – Import and select address books. Thunderbird can import address books in LDIF, TAB, CSV, TXT, and VCF formats, although results are very hit or miss. Ironically, one format Thunderbird cannot import is MAB, Thunderbird’s own native address book format. Moving address books between profiles is dated but may offer clues.

Add-ons extend Thunderbird’s functionality, making it the one of the most extensible mail clients available. To select and install them, see the add-on notes.

Plug-ins operate within Thunderbird’s built-in web browser and perform the same function they would in any browser. They are apparently shared with Firefox: every time I’ve checked I find the same plug-ins in Firefox and Thunderbird. I would just as soon my mail client not have a built-in browser, so I disable all plug-ins in Thunderbird. If I knew how, I would deactivate its built-in browser entirely.

On some Linux installations, Thunderbird stubbornly ignores my desktop environments’ default browser and requires manual configuration to make it behave.

With some mail servers, sending a message with default settings will result in the error message “Error copying mail to Sent folder” with a prompt to retry. This is an ongoing issue with my server, so until I can confirm a definitive solution, here are the suggestions I’m trying:

  • Per the University of Wisconsin, the solution is to open Menu Button – Preferences – Account Settings. In the Server Settings section of the account in question, click on the Advanced button and change “Maximum number of server connections to cache” from the default 5 to 1.
  • Per an old Thunderbird support thread, manually compact your Sent folder by right clicking on it and selecting “Compact”. If this works, you might consider reducing Thunderbird’s automatic compacting threshold to something lower than the default 20 MB in the hope that Thunderbird will then do the compacting itself before it becomes a problem. This is set in Menu Button – Preferences – Preferences – Advanced – Disk Space.

The path to Thunderbird’s per-user profile is:

  • Linux: ~/.thunderbird/x.default/
  • Windows: %sysdrive%\Users\%user%\AppData\Roaming\Thunderbird\Profiles\x.default\

…where x is a string of eight random alphanumeric characters.

I use IMAP and back up my mail on the server, so all I need to back up locally are my address books. The default address book (which appears in the user interface as “Personal Address Book”) is abook.mab. If you have more address books, they will be named abook-1.mab, abook-2.mab, and so forth.

If your backup needs exceed mine, you might find the profiles support page and MozillaZine’s profile folder page useful.

I use Thunderbird but not happily, and I am always on the lookout for a better mail client. Those I’ve tried include Claws Mail, Evolution, KMail, Balsa, and Geary.


These notes are based on Thunderbird 52.2 on Linux, and were last updated 9 August 2017.


About Warren Post

So far: Customer support guy, jungle guide, IT consultant, beach bum, entrepreneur, teacher, diplomat, over-enthusiastic cyclist. Tomorrow: who knows?
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