Thunderbird notes

This page contains notes for using Mozilla Thunderbird.

OpenPGP

Enable external GnuPG interaction (e.g. for smartcards and externally generated subkeys)

• Open the config editor (bottom of Edit -> Settings -> General)
• Change preference name mail.openpgp.allow_external_gnupg from false to true
• Enter “Add Key” dialogue (Edit -> Account Settings -> (some account) -> End-To-End Encryption -> OpenPGP -> Add Key…)
  • Select “Use your external key through GnuPG (e.g. from a smartcard)”. Click the “Continue” button.
  • Enter your primary key long ID in hexadecimal (e.g. A0A295ABDC3469C9) into the “Secret Key ID” box.
  • Press the “Save key ID” button.
• Add your public key
  • In command line, run $ gpg --export --armor --output $HOME/mypubkey.asc -- 0xA0A295ABDC3469C9 . Copy to your clipboard the resulting text from -----BEGIN PGP PUBLIC KEY BLOCK----- to -----END PGP PUBLIC KEY BLOCK-----, inclusive.
  • Open the “OpenPGP Key Manager” (Edit -> Account Settings -> (some account) -> End-To-End Encryption -> OpenPGP -> OpenPGP Key Manager)
  • Edit -> Import Key(s) from Clipboard
  • If asked the question “Do you accept this key for verifying digital signatures and for encrypting messages, for all shown email addresses?”, select “Accepted (unverified)”.
  • Click “Import”.
  • In the OpenPGP Key Manager, make sure none of your expired keys from previous import operations are present (narrow columns or widen window to see the “Expiry” column).
• Restart Thunderbird (make sure to close all drafts and windows)
• When drafting a new message, enable digital signing by clicking the “OpenPGP” dropdown button, then making sure “Digitaly Sign” is has a check mark.
  • To digitally sign with an OpenPGP key by default, go to Account Settings -> End-To-End Encryption and check “Sign unencrypted messages”. To encrypt by default, select “Enable encryption for new messages”.

ISO 8601

Getting ISO 8601 date formatting into Thunderbird can be done in several ways.

ISO 8601 via Config Editor

The most direct method, available after Thunderbird 91, involves specifying date format strings in the Config Editor. This involves creating the following custom preferences:

Config Editor values for Thunderbird date formatting

Preference ID	Type	Value	Example Output
intl.date_time.pattern_override.date_short	String	yyyy-MM-dd	2026-12-31
intl.date_time.pattern_override.time_short	String	HH:mmX	23:59-08
intl.date_time.pattern_override.connector_short	String	{1}'T'{0}	2026-12-31T23:59-08

ISO 8601 via locale

Using this guide, a custom en_SE locale can be installed. A final step of # sed -i -e 's/en_SE:2000/i18n:2012/g' /usr/local/share/i18n/locales/en_SE needs to be applied as of 2026-02 on Debian-based distributions to the copy of en_SE referenced.

This method has the advantage that the custom locale applies yyyy-MM-dd formatting across any application that uses the LC_TIME environment variable, including Thunderbird.

See also

• Mozilla Thunderbird