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

Thunderbird, Postbox

Get Inbox

Change Focused Folder to the Inbox

Change the currently selected folder to your Inbox.

Compatibility: Thunderbird, Postbox SeaMonkey

Go

Show the Go Menu

Show the Go Menu

Compatibility: Thunderbird, Postbox SeaMonkey

Ignored Threads

View Ignored Threads

View all the threads in the current folder that are set as ignored.

Compatibility: Thunderbird, Postbox SeaMonkey

Insert

Show Insert Menu

Show Insert Menu

Compatibility: Thunderbird, Postbox SeaMonkey

Message

Show the Message Menu

Show the Message Menu

Compatibility: Thunderbird, Postbox SeaMonkey

Message Pane

Toggle Message Pane

Show/Hide the Message Pane.

Compatibility: Thunderbird, Postbox SeaMonkey

New Task

Add a new task to the calendar.

Add a new task to the calendar.

Compatibility: Thunderbird, Postbox SeaMonkey

Next Message

Get Real Next Message

Get the next message. Unlink the default Thunderbird buttons this just go to the next in the list, or if shift is pressed, the next unread.

Compatibility: Thunderbird, Postbox SeaMonkey

Open in Conversation

Open current message in Conversation

Open the current message in a conversation tab

Compatibility: Thunderbird, Postbox SeaMonkey

Paste As Quotation

Paste as a Quotation

Paste text so that it appears as a quoted message.

Compatibility: Thunderbird, Postbox SeaMonkey