Be careful with old versions!
These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.
Added entry to View->Header menu entry to toggle header (and to display the keyboard shortcut)
Fix problem with mail.chat.enabled preferences.
Add a new option to darken the header pane, if the message pane has focus.
Enable/disable menu items in other actions toolbar button. Added Turkish translation.
Remove padding of sidebars.
Prepare for compatibility with core support of more button tooltip text
Updated Russian translation.
Added preference to switch on/off toggling of header pane by double click. Thank you Joergen for the Danish translation. Thank you whknnn for the Chinese translation.
Double click on header pane hides/expands details.
Another try to fix the compatibility issues with Mnenhy and the problem with mail address doubling when toggling.
Fix hidden header toolbar after toggling the header.
Fix compatiblity issues with Mnenhy. Fix XUL naming issue (reviewer request).
Fix bug in wide layout. Add tooltiptext for more button in two line compact view. Clicking on more button in two line compact view expands header and all email addresses.
Move toolbar only around if necessary. Sort addresses by type (to, cc, bcc) in twoline compact header mode.
Added compatibility bugfix with mail summaries add-on: Hide header-view-toolbar in top position if appropriate.
Increase the size of the show/hide details button in the header pane.
(Hopefully) fix bug with header toolbar position
Minor cleanup: Show full URL in Linkified Subjects of RSS Feeds.
(Hopefully) switched on Danish translation of preferences dialog.
Fix for the toolbar icon problems on Mac OS X
Add-on version for TB 3.1 did reset buttons at each program start. Fixed.
Minor cleanup of show/hide details button
Add buttons of main toolbar to header pane toolbar
Added support for the (working) buttons of the Buttons! add-on (https://addons.mozilla.org/de/thunderbird/addon/106)
Add maildirect button (http://mailredirect.mozdev.org/) to message header toolbar.
Better icons for sign/encryption info in compact view header pane.