From MozillaZine Knowledge Base

This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

There are three possible sets of buttons for moving between messages:

• 'Next' and 'Previous'
• 'Next!' and 'Previous!' (if you install the Buttons! extension)
• 'Back' and 'Forward' (added in Thunderbird 2.0)

The Next and Previous buttons actually move the focus to the next or previous unread message. If you've already read that message you can't navigate there using these buttons and it looks like they're not working correctly.

You can workaround this by customizing the toolbar to remove those two buttons and replacing them with a "Next!" and a "Previous!" button which do what you expect. See this web page to download the Buttons! extension and for instructions on how to customize the toolbar. Note that if you're using Firefox as your browser you need to download the extension by right clicking on the URL and choosing "Save Link As". Otherwise Firefox will try to install the extension and give you a misleading error message.

The 'Back' and 'Forward' buttons act like a Browsers back and forward buttons. They are initially grayed out and are enabled as you've read enough messages to be able to navigate back and forth within that sequence of messages. If you find their presence confusing you can remove them by right clicking on the toolbar, selecting customize, drag and dropping those two buttons to the "Customize Toolbar" window and pressing the OK button.

If you want to keep the Previous and Next buttons you can change some of their behavior by modifying mailnews.nav_crosses_folders as follows :

0: Cross folders/groups without asking.

1: Ask for user confirmation (the default setting).

2: Stick with the current folder/group.

See Modify Thunderbird settings if you don't know how to modify settings using the config editor.

See also

• Delete a message without opening another message
• Installing extensions