How to remove the signature separator in Thunderbird

Why remove the signature separator?

When you set up a signature in Thunderbird, two dashes (--) automatically appear above it. This separator is a convention inherited from the email standards (RFC 3676), but it is not always wanted, in particular in order to:

• Keep a clean, professional layout for your emails
• Avoid visual redundancy if your signature already contains a separator
• Tailor the appearance of your messages to your own preferences
• Improve readability in certain email clients

The problem in detail

By default, Thunderbird automatically inserts a separator made up of two dashes (--) followed by a space before your signature. Here is an example of what you see:

Your message content

--
Your signature
Firstname Lastname
Email: contact@example.com

This behaviour is standard in most email clients, but it can be turned off if you prefer a different result.

Step-by-step solution

To remove the signature separator in Thunderbird for good, follow these detailed steps:

Step 1: Open Thunderbird

Launch the Thunderbird application on your operating system.

Step 2: Go to the settings

1. Click the hamburger menu ≡ at the top right of the window
2. Select Settings (or Paramètres in French)
3. In the left-hand panel, choose General (or Paramètres généraux)

Step 3: Open the Config Editor

1. Scroll to the bottom of the General settings page
2. Click the Config Editor... button (or Éditeur de configuration...)
3. Accept the warning that appears: “Caution! Changing advanced settings can affect the performance and the security of this application.”

Step 4: Change the preference

In the Config Editor search bar, type:

mail.identity.default.suppress_signature_separator

1. Double-click the matching line to change its value
2. Change the value from false to true
   • Important note: the suppress_signature_separator preference means “suppress the separator”. So true = remove (do not display) and false = display (the default behaviour)
3. The value should now appear in bold to indicate that it has been modified

Step 5: Check the result

Close the Config Editor and the settings. Create a new message to check that the separator has indeed gone.

Expected result

Once changed, your signatures will appear directly, without the dashes:

Your message content

Your signature
Firstname Lastname
Email: contact@example.com

Per-identity configuration

If you use several identities in Thunderbird (several email accounts), you can also set this option for each identity individually:

1. Open the Config Editor as described above
2. Search for mail.identity.idX.suppress_signature_separator (where X is the number of your identity)
3. Change the value to true for each identity concerned

To find the number of your identity:

• Go to Settings > Account Settings
• Select your account
• Look at the URL in the address bar or use the debugging tool

Troubleshooting

The preference does not appear

If you cannot find the mail.identity.default.suppress_signature_separator preference, you can create it manually:

1. In the Config Editor, click the + button or right-click
2. Select New > Boolean (or Nouveau > Booléen)
3. Enter the name: mail.identity.default.suppress_signature_separator
4. Set the value to true

The separator comes back after an update

If the separator comes back after a Thunderbird update, check that the preference is still set to true in the Config Editor. Major updates can sometimes reset certain preferences.

The change does not take effect immediately

Sometimes you need to:

• Close Thunderbird completely and reopen it
• Create a new message (messages that are already open may keep the old format)

Compatibility

This solution works on:

• Thunderbird 115 (the latest version)
• Earlier versions (102 and above)
• All operating systems: Windows, macOS, Linux

Alternative: making the change through about:config

If you prefer to use the about:config interface directly:

1. Open Thunderbird
2. Use the quick search bar:
   • Press Ctrl+K (or Cmd+K on a Mac) to open the quick search bar
   • Or use the Tools > Quick Search menu
3. Type about:config in the search bar and press Enter
4. Accept the warning that appears
5. Search for mail.identity.default.suppress_signature_separator in the search field
6. Double-click the matching line to switch the value to true (to remove the separator)

Note: this method is equivalent to using the Config Editor from Settings. Both methods reach the same advanced configuration preferences.

Additional resources

• Official Thunderbird documentation
• RFC 3676 - Signature standard
• Thunderbird community forum

This change lets you tailor the appearance of your emails to your own preferences, while keeping every other Thunderbird feature intact.