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

Thunderbird, Postbox

Rewrap

Rewraps the message text

Install Rewrap

Download Rewrap

Compatibility: Thunderbird, Postbox SeaMonkey

Send & Receive

Send all messages in the outbox and get all new messages.

Install Send & Receive

Download Send & Receive

Compatibility: Thunderbird, Postbox SeaMonkey

Skip Trash

Delete a message with out sending it to the Trash. This will completely remove the message so that it can not be recovered.

Install Skip Trash

Download Skip Trash

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

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

Watched Threads with Unread

View watched threads that have unread messages in them.

Install Watched Threads with Unread

Download Watched Threads with Unread

Compatibility: Thunderbird, Postbox SeaMonkey