These are a ready make selection of some of the most popular buttons from the Custom Toolbar Button Maker

Thunderbird, Postbox

Remote Content

Opens the window to set exceptions for the loading of remote content

Install Remote Content

Download Remote Content

Compatibility: Thunderbird, Postbox SeaMonkey

Reply to Sender Only

Reply only to the sender of the email.

Install Reply to Sender Only

Download Reply to Sender Only

Compatibility: Thunderbird, Postbox SeaMonkey

Rewrap

Rewraps the message text

Install Rewrap

Download Rewrap

Compatibility: Thunderbird, Postbox SeaMonkey

Tasks In View

Toggle the Task in View panel in Sunbird.

Install Tasks In View

Download Tasks In View

Compatibility: Thunderbird, Postbox SeaMonkey

Threads with Unread

View only the threads in the current folder that have unread messages.

Install Threads with Unread

Download Threads with Unread

Compatibility: Thunderbird, Postbox SeaMonkey

Toggle Starred

Toggle the starred status (look for the star next to the message).

Install Toggle Starred

Download Toggle Starred

Compatibility: Thunderbird, Postbox SeaMonkey

Unread Threads

View threads that you have not read yet.

Install Unread Threads

Download Unread Threads

Compatibility: Thunderbird, Postbox SeaMonkey